Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2022	Oct. 31, 2022
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2022
Document Transition Report	false
Entity File Number	1-14756
Entity Registrant Name	Ameren Corporation
Entity Tax Identification Number	43-1723446
Entity Incorporation, State or Country Code	MO
Entity Address, Address Line One	1901 Chouteau Avenue
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63103
City Area Code	(314)
Local Phone Number	621-3222
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol(s)	AEE
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Emerging growth company	false
Entity Shell Company	false
Shares outstanding		258,522,169
Entity Central Index Key	0001002910
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Amendment Flag	false
Union Electric Company
Entity Information [Line Items]
Entity File Number	1-2967
Entity Registrant Name	Union Electric Company
Entity Tax Identification Number	43-0559760
Entity Incorporation, State or Country Code	MO
Entity Address, Address Line One	1901 Chouteau Avenue
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63103
City Area Code	(314)
Local Phone Number	621-3222
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Emerging growth company	false
Entity Shell Company	false
Shares outstanding		102,123,834
Entity Central Index Key	0000100826
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Amendment Flag	false
Ameren Illinois Company
Entity Information [Line Items]
Entity File Number	1-3672
Entity Registrant Name	Ameren Illinois Company
Entity Tax Identification Number	37-0211380
Entity Incorporation, State or Country Code	IL
Entity Address, Address Line One	10 Richard Mark Way
Entity Address, City or Town	Collinsville
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	62234
City Area Code	(618)
Local Phone Number	343-8150
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Emerging growth company	false
Entity Shell Company	false
Shares outstanding		25,452,373
Entity Central Index Key	0000018654
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Amendment Flag	false
Ameren Illinois Company \| Former Address
Entity Information [Line Items]
Entity Address, Address Line One	10 Executive Drive
Entity Address, City or Town	Collinsville
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	62234

Consolidated Statement of Income (Loss) and Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating Revenues:
Total operating revenues	$ 2,306	$ 1,811	$ 5,911	$ 4,849
Operating Expenses:
Fuel	117	184	376	422
Purchased power	563	159	1,058	479
Natural gas purchased for resale	58	45	431	275
Other operations and maintenance	475	457	1,427	1,289
Depreciation and amortization	350	290	965	856
Taxes other than income taxes	144	142	415	392
Total operating expenses	1,707	1,277	4,672	3,713
Operating Income	599	534	1,239	1,136
Other Income, Net	58	56	180	151
Interest Charges	126	94	356	290
Income Before Income Taxes	531	496	1,063	997
Income Taxes	78	70	148	128
Net Income	453	426	915	869
Less: Net Income Attributable to Noncontrolling Interests	1	1	4	4
Net Income Attributable to Ameren Common Shareholders	452	425	911	865
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	0	1	1	1
Comprehensive Income	453	427	916	870
Less: Comprehensive Income Attributable to Noncontrolling Interests	1	1	4	4
Comprehensive Income Attributable to Ameren Common Shareholders	$ 452	$ 426	$ 912	$ 866
Earnings Per Share, Basic and Diluted [Abstract]
Earnings per Common Share – Basic	$ 1.75	$ 1.66	$ 3.53	$ 3.38
Earnings per Common Share – Diluted	$ 1.74	$ 1.65	$ 3.51	$ 3.36
Weighted-average Common Shares Outstanding – Basic	258.4	257.3	258.2	255.9
Weighted-average Common Shares Outstanding – Diluted	259.5	258.6	259.3	257.2
Electric
Operating Revenues:
Total operating revenues	$ 2,140	$ 1,668	$ 4,971	$ 4,108
Natural gas
Operating Revenues:
Total operating revenues	166	143	940	741
Union Electric Company
Operating Revenues:
Total operating revenues	1,359	1,129	3,096	2,642
Operating Expenses:
Fuel	117	184	376	422
Purchased power	247	57	458	195
Natural gas purchased for resale	7	4	65	40
Other operations and maintenance	252	240	744	683
Depreciation and amortization	208	161	550	474
Taxes other than income taxes	106	104	281	266
Total operating expenses	937	750	2,474	2,080
Operating Income	422	379	622	562
Other Income, Net	25	27	72	74
Interest Charges	58	32	157	107
Income Before Income Taxes	389	374	537	529
Income Taxes	(9)	(2)	(13)	(7)
Net Income	398	376	550	536
Preferred Stock Dividends	1	1	3	3
Net Income Attributable to Parent	397	375	547	533
Union Electric Company \| Electric
Operating Revenues:
Total operating revenues	1,338	1,113	2,966	2,543
Union Electric Company \| Natural gas
Operating Revenues:
Total operating revenues	21	16	130	99
Ameren Illinois Company
Operating Revenues:
Total operating revenues	904	645	2,697	2,097
Operating Expenses:
Purchased power	319	108	608	298
Natural gas purchased for resale	51	41	366	235
Other operations and maintenance	215	217	663	604
Depreciation and amortization	130	118	382	350
Taxes other than income taxes	34	34	122	114
Total operating expenses	749	518	2,141	1,601
Operating Income	155	127	556	496
Other Income, Net	26	19	75	49
Interest Charges	42	41	125	123
Income Before Income Taxes	139	105	506	422
Income Taxes	36	26	130	107
Net Income	103	79	376	315
Preferred Stock Dividends	0	0	1	1
Net Income Attributable to Parent	103	79	375	314
Ameren Illinois Company \| Electric
Operating Revenues:
Total operating revenues	758	518	1,886	1,455
Ameren Illinois Company \| Natural gas
Operating Revenues:
Total operating revenues	$ 146	$ 127	$ 811	$ 642

Consolidated Statement of Income (Loss) and Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Statement [Abstract]
Pension and other postretirement benefit plan activity, tax	$ 0	$ 0	$ 0	$ 0

Consolidated Balance Sheet - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Current Assets:
Cash and cash equivalents	$ 7	$ 8
Accounts receivable - trade (less allowance for doubtful accounts)	665	434
Unbilled revenue	366	301
Miscellaneous accounts receivable	62	85
Inventories	695	592
Current regulatory assets	346	319
Current collateral assets	145	66
Other current assets	232	163
Total current assets	2,518	1,968
Property, Plant, and Equipment, Net	30,608	29,261
Investments and Other Assets:
Nuclear decommissioning trust fund	910	1,159
Goodwill	411	411
Regulatory assets	1,405	1,289
Pension and other postretirement benefits	813	756
Other assets	992	891
Total investments and other assets	4,531	4,506
TOTAL ASSETS	37,657	35,735
Current Liabilities:
Current maturities of long-term debt	155	505
Short-term debt	1,221	545
Accounts and wages payable	820	1,095
Taxes accrued	216	74
Current regulatory liabilities	179	113
Other current liabilities	584	494
Total current liabilities	3,175	2,826
Long-term Debt, Net	13,577	12,562
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	3,785	3,499
Regulatory liabilities	5,658	5,848
Asset retirement obligations	771	757
Other deferred credits and liabilities	361	414
Total deferred credits and other liabilities	10,575	10,518
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	3	3
Other paid-in capital, principally premium on common stock	6,548	6,502
Retained earnings	3,636	3,182
Accumulated other comprehensive income	14	13
Total shareholders’ equity	10,201	9,700
Noncontrolling Interests	129	129
Total equity	10,330	9,829
TOTAL LIABILITIES AND EQUITY	37,657	35,735
Union Electric Company
Current Assets:
Cash and cash equivalents	0	0
Accounts receivable - trade (less allowance for doubtful accounts)	302	190
Accounts receivable – affiliates	23	44
Unbilled revenue	204	142
Miscellaneous accounts receivable	39	71
Inventories	438	419
Current regulatory assets	243	127
Current collateral assets	140	66
Other current assets	99	76
Total current assets	1,488	1,135
Property, Plant, and Equipment, Net	15,829	15,296
Investments and Other Assets:
Nuclear decommissioning trust fund	910	1,159
Regulatory assets	642	523
Pension and other postretirement benefits	223	208
Other assets	425	401
Total investments and other assets	2,200	2,291
TOTAL ASSETS	19,517	18,722
Current Liabilities:
Current maturities of long-term debt	55	55
Short-term debt	178	165
Accounts and wages payable	339	631
Accounts payable – affiliates	43	46
Taxes accrued	183	34
Interest accrued	69	60
Mark-to-market derivative liabilities	113	53
Current regulatory liabilities	87	57
Other current liabilities	114	116
Total current liabilities	1,181	1,217
Long-term Debt, Net	6,085	5,564
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	1,952	1,852
Regulatory liabilities	3,004	3,354
Asset retirement obligations	767	753
Other deferred credits and liabilities	70	71
Total deferred credits and other liabilities	5,793	6,030
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	511	511
Other paid-in capital, principally premium on common stock	2,725	2,725
Preferred stock	80	80
Retained earnings	3,142	2,595
Total shareholders’ equity	6,458	5,911
TOTAL LIABILITIES AND EQUITY	19,517	18,722
Ameren Illinois Company
Current Assets:
Cash and cash equivalents	0	0
Accounts receivable - trade (less allowance for doubtful accounts)	349	228
Accounts receivable – affiliates	9	24
Unbilled revenue	162	159
Miscellaneous accounts receivable	14	1
Inventories	257	173
Mark-to-market derivative assets	68	28
Current regulatory assets	100	180
Other current assets	39	30
Total current assets	998	823
Property, Plant, and Equipment, Net	13,011	12,223
Investments and Other Assets:
Goodwill	411	411
Regulatory assets	742	752
Pension and other postretirement benefits	456	427
Other assets	514	399
Total investments and other assets	2,123	1,989
TOTAL ASSETS	16,132	15,035
Current Liabilities:
Current maturities of long-term debt	100	400
Short-term debt	353	103
Accounts and wages payable	394	361
Accounts payable – affiliates	117	64
Current regulatory liabilities	92	54
Other current liabilities	275	251
Total current liabilities	1,331	1,233
Long-term Debt, Net	4,389	3,992
Deferred Credits and Other Liabilities:
Accumulated deferred income taxes and tax credits, net	1,670	1,558
Regulatory liabilities	2,532	2,374
Other deferred credits and liabilities	195	238
Total deferred credits and other liabilities	4,397	4,170
Commitments and Contingencies
Shareholders’ Equity:
Common Stock	0	0
Other paid-in capital, principally premium on common stock	2,914	2,914
Preferred stock	49	49
Retained earnings	3,052	2,677
Total shareholders’ equity	6,015	5,640
TOTAL LIABILITIES AND EQUITY	$ 16,132	$ 15,035

Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Accounts Receivable, Allowance for Credit Loss, Current	$ 31	$ 29
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	400,000,000.0	400,000,000.0
Common Stock, Shares, Outstanding	258,500,000	257,700,000
Union Electric Company
Accounts Receivable, Allowance for Credit Loss, Current	$ 12	$ 13
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	150,000,000.0	150,000,000.0
Common Stock, Shares, Outstanding	102,100,000	102,100,000
Ameren Illinois Company
Accounts Receivable, Allowance for Credit Loss, Current	$ 19	$ 16
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	45,000,000.0	45,000,000.0
Common Stock, Shares, Outstanding	25,500,000	25,500,000

Consolidated Statement of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash Flows From Operating Activities:
Net income	$ 915	$ 869
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,016	903
Amortization of nuclear fuel	46	37
Amortization of debt issuance costs and premium/discounts	17	17
Deferred income taxes and investment tax credits, net	137	139
Allowance for equity funds used during construction	(31)	(30)
Stock-based compensation costs	18	17
Other	63	11
Changes in assets and liabilities:
Receivables	(296)	(212)
Inventories	(103)	(73)
Accounts and wages payable	(128)	(143)
Taxes accrued	147	148
Regulatory assets and liabilities	(17)	(340)
Assets, other	(87)	(58)
Liabilities, other	19	(35)
Pension and other postretirement benefits	(49)	(6)
Counterparty collateral, net	(68)	(52)
Net cash provided by operating activities	1,599	1,192
Cash Flows From Investing Activities:
Capital expenditures	(2,437)	(2,613)
Nuclear fuel expenditures	(22)	(19)
Purchases of securities – nuclear decommissioning trust fund	(176)	(411)
Sales and maturities of securities – nuclear decommissioning trust fund	163	404
Other	14	(7)
Net cash used in investing activities	(2,458)	(2,646)
Cash Flows From Financing Activities:
Dividends on common stock	(457)	(423)
Dividends paid to noncontrolling interest holders	(4)	(4)
Short-term debt, net	675	63
Maturities of long-term debt	(450)	0
Issuances of long-term debt	1,118	1,423
Issuances of common stock	29	297
Redemptions of Ameren Illinois preferred stock	0	(13)
Employee payroll taxes related to stock-based compensation	(16)	(17)
Debt issuance costs	(11)	(15)
Other	0	(13)
Net cash provided by financing activities	884	1,298
Net change in cash, cash equivalents, and restricted cash	25	(156)
Cash, cash equivalents, and restricted cash at beginning of year	155	301
Cash, cash equivalents, and restricted cash at end of period	180	145
Union Electric Company
Cash Flows From Operating Activities:
Net income	550	536
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	603	522
Amortization of nuclear fuel	46	37
Amortization of debt issuance costs and premium/discounts	5	5
Deferred income taxes and investment tax credits, net	(17)	(7)
Allowance for equity funds used during construction	(17)	(17)
Other	9	8
Changes in assets and liabilities:
Receivables	(160)	(216)
Inventories	(19)	(19)
Accounts and wages payable	(192)	(145)
Taxes accrued	161	146
Regulatory assets and liabilities	(164)	(164)
Assets, other	(9)	20
Liabilities, other	14	(9)
Pension and other postretirement benefits	(12)	6
Counterparty collateral, net	(72)	(58)
Net cash provided by operating activities	726	645
Cash Flows From Investing Activities:
Capital expenditures	(1,237)	(1,567)
Nuclear fuel expenditures	(22)	(19)
Purchases of securities – nuclear decommissioning trust fund	(176)	(411)
Sales and maturities of securities – nuclear decommissioning trust fund	163	404
Money pool advances, net	0	115
Other	17	0
Net cash used in investing activities	(1,255)	(1,478)
Cash Flows From Financing Activities:
Dividends on preferred stock	(3)	(3)
Short-term debt, net	13	0
Issuances of long-term debt	524	524
Capital contributions from parent	0	183
Debt issuance costs	(6)	(5)
Net cash provided by financing activities	528	699
Net change in cash, cash equivalents, and restricted cash	(1)	(134)
Cash, cash equivalents, and restricted cash at beginning of year	8	145
Cash, cash equivalents, and restricted cash at end of period	7	11
Ameren Illinois Company
Cash Flows From Operating Activities:
Net income	376	315
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	381	349
Amortization of debt issuance costs and premium/discounts	9	10
Deferred income taxes and investment tax credits, net	92	134
Allowance for equity funds used during construction	(14)	(13)
Other	19	8
Changes in assets and liabilities:
Receivables	(138)	8
Inventories	(84)	(54)
Accounts and wages payable	62	12
Taxes accrued	54	(21)
Regulatory assets and liabilities	147	(167)
Assets, other	(75)	(59)
Liabilities, other	35	1
Pension and other postretirement benefits	(29)	(16)
Net cash provided by operating activities	835	507
Cash Flows From Investing Activities:
Capital expenditures	(1,145)	(1,026)
Money pool advances, net	0	(41)
Other	0	(7)
Net cash used in investing activities	(1,145)	(1,074)
Cash Flows From Financing Activities:
Dividends on preferred stock	(1)	(1)
Short-term debt, net	250	0
Money pool borrowings, net	0	(19)
Maturities of long-term debt	(400)	0
Issuances of long-term debt	499	449
Capital contributions from parent	0	145
Redemption of preferred stock	0	(13)
Debt issuance costs	(5)	(6)
Other	0	(13)
Net cash provided by financing activities	343	542
Net change in cash, cash equivalents, and restricted cash	33	(25)
Cash, cash equivalents, and restricted cash at beginning of year	133	147
Cash, cash equivalents, and restricted cash at end of period	$ 166	$ 122

Consolidated Statement of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Other Paid-in Capital	Retained Earnings	Deferred Retirement Benefit Costs	Accumulated Other Comprehensive Income	Total Ameren Corporation Shareholders' Equity	Noncontrolling Interests	Union Electric Company	Union Electric Company Common Stock	Union Electric Company Other Paid-in Capital	Union Electric Company Preferred Stock	Union Electric Company Retained Earnings	Ameren Illinois Company	Ameren Illinois Company Common Stock	Ameren Illinois Company Other Paid-in Capital	Ameren Illinois Company Preferred Stock	Ameren Illinois Company Retained Earnings
Beginning of period at Dec. 31, 2020			$ 6,179	$ 2,757	$ (1)			$ 142			$ 2,518		$ 2,101			$ 2,652	$ 62	$ 2,252
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Settlement of forward sale agreement through common shares issuance			113
Shares issued under the ATM program			148
Shares issued under the DRPlus and 401(k) plan			36
Stock-based compensation activity			7
Capital contributions from parent									$ 183		183			$ 145		145
Net income	$ 869								536				536	315				315
Net income attributable to Ameren common shareholders	865			865
Dividends on common stock				(423)
Preferred stock dividends													(3)					(1)
Change in deferred retirement benefit costs	1				1
Net income attributable to noncontrolling interest holders	$ (4)							4
Dividends paid to noncontrolling interest holders								(4)
Redemptions of preferred stock								(13)									(13)
Common stock shares outstanding at beginning of year (in shares) at Dec. 31, 2020	253,300,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under forward sale agreement (in shares)	1,600,000
Stock Issued During Period, Shares, New Issues	1,800,000
Shares issued under the DRPlus and 401(k) plan	400,000
Shares issued for stock-based compensation (in shares)	500,000
Common stock shares outstanding at end of period (in shares) at Sep. 30, 2021	257,600,000
End of period at Sep. 30, 2021	$ 9,814	$ 3	6,483	3,199	0	$ 0		129		$ 511	2,701	$ 80	2,634		$ 0	2,797	49	2,566
Shareholders' equity, end of year at Sep. 30, 2021							$ 9,685		5,926					5,412
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share (in dollars per share)	$ 1.65
Beginning of period at Jun. 30, 2021			6,436	2,915	(1)			129			2,701		2,259			2,722	49	2,487
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Settlement of forward sale agreement through common shares issuance			0
Shares issued under the ATM program			27
Shares issued under the DRPlus and 401(k) plan			12
Stock-based compensation activity			8
Capital contributions from parent											0					75
Net income	$ 426								376				376	79				79
Net income attributable to Ameren common shareholders	425			425
Dividends on common stock				(141)
Preferred stock dividends													(1)					0
Change in deferred retirement benefit costs	1				1
Net income attributable to noncontrolling interest holders	$ (1)							1
Dividends paid to noncontrolling interest holders								(1)
Redemptions of preferred stock								0									0
Common stock shares outstanding at beginning of year (in shares) at Jun. 30, 2021	257,100,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under forward sale agreement (in shares)	0
Stock Issued During Period, Shares, New Issues	400,000
Shares issued under the DRPlus and 401(k) plan	100,000
Shares issued for stock-based compensation (in shares)	0
Common stock shares outstanding at end of period (in shares) at Sep. 30, 2021	257,600,000
End of period at Sep. 30, 2021	$ 9,814	3	6,483	3,199	0	0		129		511	2,701	80	2,634		0	2,797	49	2,566
Shareholders' equity, end of year at Sep. 30, 2021							9,685		5,926					5,412
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share (in dollars per share)	$ 0.55
Beginning of period at Dec. 31, 2021	$ 9,829		6,502	3,182	13			129			2,725		2,595			2,914	49	2,677
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Settlement of forward sale agreement through common shares issuance			0
Shares issued under the ATM program			0
Shares issued under the DRPlus and 401(k) plan			37
Stock-based compensation activity			9
Capital contributions from parent									0		0			0		0
Net income	915								$ 550				550	$ 376				376
Net income attributable to Ameren common shareholders	911			911
Dividends on common stock				(457)
Preferred stock dividends													(3)					(1)
Change in deferred retirement benefit costs	1				1
Net income attributable to noncontrolling interest holders	$ (4)							4
Dividends paid to noncontrolling interest holders								(4)
Redemptions of preferred stock								0									0
Common stock shares outstanding at beginning of year (in shares) at Dec. 31, 2021	257,700,000								102,100,000					25,500,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under forward sale agreement (in shares)	0
Stock Issued During Period, Shares, New Issues	0
Shares issued under the DRPlus and 401(k) plan	400,000
Shares issued for stock-based compensation (in shares)	400,000
Common stock shares outstanding at end of period (in shares) at Sep. 30, 2022	258,500,000								102,100,000					25,500,000
End of period at Sep. 30, 2022	$ 10,330	3	6,548	3,636	14	14		129		511	2,725	80	3,142		0	2,914	49	3,052
Shareholders' equity, end of year at Sep. 30, 2022	$ 10,201						10,201		$ 6,458					$ 6,015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share (in dollars per share)	$ 1.77
Beginning of period at Jun. 30, 2022			6,527	3,336	14			129			2,725		2,745			2,914	49	2,949
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Settlement of forward sale agreement through common shares issuance			0
Shares issued under the ATM program			0
Shares issued under the DRPlus and 401(k) plan			12
Stock-based compensation activity			9
Capital contributions from parent											0					0
Net income	$ 453								$ 398				398	$ 103				103
Net income attributable to Ameren common shareholders	452			452
Dividends on common stock				(152)
Preferred stock dividends													(1)					0
Change in deferred retirement benefit costs	0				0
Net income attributable to noncontrolling interest holders	$ (1)							1
Dividends paid to noncontrolling interest holders								(1)
Redemptions of preferred stock								0									0
Common stock shares outstanding at beginning of year (in shares) at Jun. 30, 2022	258,400,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under forward sale agreement (in shares)	0
Stock Issued During Period, Shares, New Issues	0
Shares issued under the DRPlus and 401(k) plan	100,000
Shares issued for stock-based compensation (in shares)	0
Common stock shares outstanding at end of period (in shares) at Sep. 30, 2022	258,500,000								102,100,000					25,500,000
End of period at Sep. 30, 2022	$ 10,330	$ 3	$ 6,548	$ 3,636	$ 14	$ 14		$ 129		$ 511	$ 2,725	$ 80	$ 3,142		$ 0	$ 2,914	$ 49	$ 3,052
Shareholders' equity, end of year at Sep. 30, 2022	$ 10,201						$ 10,201		$ 6,458					$ 6,015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share (in dollars per share)	$ 0.59

Summary Of Significant Accounting Policies	9 Months Ended
Summary Of Significant Accounting Policies	Sep. 30, 2022
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES General Ameren, headquartered in St. Louis, Missouri, is a public utility holding company whose primary assets are its equity interests in its subsidiaries. Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. Dividends on Ameren’s common stock and the payment of expenses by Ameren depend on distributions made to it by its subsidiaries. Ameren’s principal subsidiaries are listed below. Ameren has other subsidiaries that conduct other activities, such as providing shared services. •Union Electric Company, doing business as Ameren Missouri, operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri. •Ameren Illinois Company, doing business as Ameren Illinois, operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois. •ATXI operates a FERC rate-regulated electric transmission business in the MISO. Due to a change in customer behavior and certain business practices resulting from the COVID-19 pandemic, there has been a shift in sales volumes by customer class at both Ameren Missouri and Ameren Illinois, which began in 2020, with an increase in residential sales, and a decrease in commercial and industrial sales. While our electric sales volumes in the first nine months of 2022, excluding the estimated effects of weather and customer energy-efficiency programs, were comparable to the same period in 2021 and, at Ameren Missouri, were comparable to pre-pandemic levels, Ameren Illinois’ sales volumes remain below pre-pandemic levels. However, revenues from Ameren Illinois’ electric distribution business, residential and small nonresidential customers of Ameren Illinois’ natural gas distribution business, and Ameren Illinois’ and ATXI’s electric transmission businesses are decoupled from changes in sales volumes. Earnings at Ameren Missouri and those associated with Ameren Illinois’ large nonresidential natural gas customers are exposed to such changes. Further effects of the COVID-19 pandemic on our results of operations, financial position, and liquidity in subsequent periods will depend on its severity and longevity, future regulatory or legislative actions with respect thereto, and the resulting impact on business, economic, and capital market conditions. Ameren’s and Ameren Missouri’s financial statements are prepared on a consolidated basis and therefore include the accounts of their majority-owned subsidiaries. All intercompany transactions have been eliminated. Ameren Missouri’s subsidiaries were created for the ownership of renewable generation projects. Ameren Illinois has no subsidiaries. All tabular dollar amounts are in millions, unless otherwise indicated. Our accounting policies conform to GAAP. Our financial statements reflect all adjustments (which include normal, recurring adjustments) that are necessary, in our opinion, for a fair presentation of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. The results of operations for an interim period may not give a true indication of results that may be expected for a full year. These financial statements should be read in conjunction with the financial statements and accompanying notes included in the Form 10-K. Variable Interest Entities As of September 30, 2022, and December 31, 2021, Ameren had unconsolidated variable interests as a limited partner in various equity method investments, primarily to advance clean and resilient energy technologies, totaling $58 million and $56 million, respectively, included in “Other assets” on Ameren’s consolidated balance sheet. Any earnings or losses related to these investments are included in “Other Income, Net” on Ameren’s consolidated statement of income and comprehensive income. Ameren is not the primary beneficiary of these investments because it does not have the power to direct matters that most significantly affect the activities of these variable interest entities. As of September 30, 2022, the maximum exposure to loss related to these variable interests is limited to the investment in these partnerships of $58 million plus associated outstanding funding commitments of $21 million. COLI Ameren and Ameren Illinois have COLI, which is recorded at the net cash surrender value. The net cash surrender value is the amount that can be realized under the insurance policies at the balance sheet date. As of September 30, 2022, the cash surrender value of COLI at Ameren and Ameren Illinois was $239 million (December 31, 2021 – $278 million) and $116 million (December 31, 2021 – $117 million), respectively, while total borrowings against the policies were $108 million (December 31, 2021 – $109 million) at both Ameren and Ameren Illinois. Ameren and Ameren Illinois have the right to offset the borrowings against the cash surrender value of the policies and, consequently, present the net asset in “Other assets” on their respective balance sheets. The net cash surrender value of Ameren’s COLI is affected by the investment performance of a separate account in which Ameren holds a beneficial interest.

Rate And Regulatory Matters	9 Months Ended
Rate And Regulatory Matters	Sep. 30, 2022
Public Utilities, General Disclosures [Abstract]
RATE AND REGULATORY MATTERS	RATE AND REGULATORY MATTERS Below is a summary of updates to significant regulatory proceedings and related legal proceedings. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of the Form 10-K for additional information and a summary of our regulatory frameworks. We are unable to predict the ultimate outcome of these matters, the timing of final decisions of the various agencies and courts, or the impact on our results of operations, financial position, or liquidity. Missouri 2022 Electric Service Regulatory Rate Review In August 2022, Ameren Missouri filed a request with the MoPSC seeking approval to increase its annual revenues for electric service by $316 million. The electric rate increase request is based on a 10.2% ROE, a capital structure composed of 51.9% common equity, a rate base of $11.6 billion, and a test year ended March 31, 2022, with certain pro-forma adjustments expected through an anticipated true-up date of December 31, 2022. Ameren Missouri’s request includes the continued use of the FAC and trackers for pension and postretirement benefits, uncertain income tax positions, certain excess deferred income taxes, and renewable energy standard costs that the MoPSC previously authorized in earlier electric rate orders, as well as the use of an electric property tax tracker allowed under Missouri Senate Bill 745 discussed below. In October 2022, Ameren Missouri also requested the use of a tracker for variances between actual income tax benefits and costs resulting from the IRA and those amounts included in customer rates, which would be considered for recovery or refund in a future electric regulatory rate review. For additional information regarding the IRA, see Note 12 – Income Taxes. The electric rate increase request reflects the following: •increased infrastructure investments made under Ameren Missouri’s Smart Energy Plan, including increased cost of capital and depreciation expense; •increased net fuel expense due to reduced off system sales, primarily driven by expected reduced operations at the Rush Island Energy Center; and •extending the retirement date of the Sioux Energy Center from 2028 to 2030, consistent with Ameren Missouri’s 2022 Change to the 2020 IRP, in order to support reliability during the transition to clean energy generation. In connection with the planned accelerated retirement of the Rush Island Energy Center, Ameren Missouri expects to seek approval from the MoPSC to finance the costs associated with the retirement, including the remaining unrecovered net plant balance associated with the facility, through the issuance of securitized utility tariff bonds pursuant to the Missouri securitization statute. As such, Ameren Missouri did not request a change in the depreciation rates related to the Rush Island Energy Center in this electric service regulatory rate review. The MoPSC proceeding relating to the proposed electric service rate changes will take place over a period of up to 11 months, with a decision by the MoPSC expected by June 2023 and new rates effective by July 2023. Ameren Missouri cannot predict the level of any electric service rate change the MoPSC may approve, whether the requested regulatory recovery mechanisms will be approved, or whether any rate change that may eventually be approved will be sufficient for Ameren Missouri to recover its costs and earn a reasonable return on its investments when the rate change goes into effect. Missouri Senate Bill 745 In June 2022, Missouri Senate Bill 745 was enacted and became effective on August 28, 2022. The law extended Ameren Missouri’s PISA election through December 2028 and allows for an additional extension through December 2033 if requested by Ameren Missouri and approved by the MoPSC, among other things. The law established a 2.5% annual limit on increases to the electric service revenue requirement used to set customer rates due to the inclusion of incremental PISA deferrals in the revenue requirement. The limitation will be effective for revenue requirements approved by the MoPSC after January 1, 2024, and will be based on the revenue requirement established in the immediately preceding rate order. The current rate limitation, which is effective through 2023, is a 2.85% cap on the compound annual growth rate in the average overall customer rate per kilowatthour, based on the electric rates that became effective in April 2017, less half of the annual savings from the TCJA that was passed on to customers as approved in a July 2018 MoPSC order. The law also established electric and natural gas property tax trackers that allow Ameren Missouri to defer the difference between actual property taxes incurred and related taxes included in customer rates as a regulatory asset or regulatory liability, with the difference expected to be reflected in rate base in a subsequent rate order. Upon the effective date of the law, Ameren Missouri began deferring amounts under these trackers. The deferrals were immaterial as of September 30, 2022. Solar Generation Facilities In February 2022, Ameren Missouri, through a subsidiary, entered into a build-transfer agreement to acquire, after construction, a 150-MW solar generation facility, which is expected to be located in southeastern Illinois and, if approved by the MoPSC, to serve customers under Ameren Missouri’s Renewable Solutions Program discussed below. In June 2022, Ameren Missouri, through a subsidiary, entered into a build-transfer agreement to acquire, after construction, a 200-MW solar generation facility, which is expected to be located in central Missouri and support Ameren Missouri’s compliance with the state of Missouri’s requirement of achieving 15% of retail sales from renewable energy sources, of which 2% must be derived from solar energy sources. The acquisitions are aligned with the 2022 Change to the 2020 IRP, which Ameren Missouri filed with the MoPSC in June 2022, and are subject to certain conditions, including the issuance of certificates of convenience and necessity by the MoPSC, obtaining MISO transmission interconnection agreements, and approval by the FERC. In July 2022, Ameren Missouri filed for certificates of convenience and necessity with the MoPSC for both facilities and expects decisions by March 2023 and April 2023 for the 200-MW facility and the 150-MW facility, respectively. Depending on the timing of regulatory approvals and the impact of potential sourcing issues resulting from a United States Department of Commerce investigation of solar panels imported from four Southeast Asian countries initiated in late March 2022 and the detention of certain solar panels sourced from China as a result of the Uyghur Forced Labor Prevention Act that was passed in December 2021, the projects could be completed as early as the fourth quarter of 2024. Renewable Solutions Program In July 2022, Ameren Missouri filed a request with the MoPSC seeking approval of its Renewable Solutions Program and a tariff related to participation in the program. The program would allow certain commercial, industrial, and governmental customers to receive up to 100% of their energy from renewable resources. Based on customer contracts, the program would enable Ameren Missouri to supply renewable solar energy generated by the 150-MW facility discussed above to customers that enroll in the program. Ameren Missouri expects a decision from the MoPSC by April 2023. MoPSC Staff Review of Planned Rush Island Energy Center Retirement In February 2022, the MoPSC issued an order directing the MoPSC staff to review Ameren Missouri’s planned accelerated retirement of the Rush Island Energy Center as a result of the NSR and Clean Air Act Litigation discussed in Note 9 – Commitments and Contingencies. The MoPSC staff’s review includes potential impacts on the reliability and cost of Ameren Missouri’s service to its customers; Ameren Missouri’s plans to mitigate the customer impacts of the accelerated retirement; and the prudence of Ameren Missouri’s actions and decisions with regard to the Rush Island Energy Center, which is expected to be addressed in the 2022 electric service regulatory rate review, among other things. In April 2022, the MoPSC staff filed an initial report with the MoPSC in which the staff concluded early retirement of the Rush Island Energy Center may cause reliability concerns. The MoPSC staff is under no deadline to complete this review. Ameren Missouri is unable to predict the results of this matter. Results of the review could be used in other MoPSC proceedings, which could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. MEEIA In August 2022, the MoPSC issued an order approving Ameren Missouri’s energy savings results for the 2021 program year of the MEEIA 2019 program. As a result of this order and a MoPSC order issued in September 2021, Ameren Missouri recognized revenues of $12 million and $9 million in the third quarter of 2022 and 2021, respectively. December 2021 MoPSC Electric and Natural Gas Rate Orders In December 2021, the MoPSC issued orders in Ameren Missouri’s 2021 electric service and natural gas delivery service regulatory rate reviews. The new electric and natural gas rates approved by these orders became effective on February 28, 2022. Illinois MYRP ROE Performance Metrics Under an MYRP, the ROE approved by the ICC would be subject to annual adjustments during the four-year period based on certain performance metrics, with aggregate symmetrical performance-based ROE incentives and penalties ranging from 20 to 60 basis points annually. In September 2022, the ICC issued an order approving the performance metrics to be used by Ameren Illinois in determining ROE incentives and penalties. The ICC order approved total ROE incentives and penalties of 24 basis points, allocated among seven approved performance metrics. These performance metrics include improvements in service reliability in both the frequency and duration of outages, a reduction in peak loads, an increased percentage of spend with diverse suppliers, a reduction in disconnections for certain customers, and improved timeliness in response to customer requests for interconnection of distributed energy resources. The ROE incentives and penalties would apply annually from 2024 through 2027 if, as planned, Ameren Illinois elects to file an MYRP by January 20, 2023. Electric Distribution Service Rates Under IEIMA In April 2022, Ameren Illinois filed its annual electric distribution service performance-based formula rate update with the ICC to be used for 2023 rates. In July 2022, Ameren Illinois filed a revised request seeking to increase its annual revenues for electric distribution service by $84 million. The updated request reflects an increase to the annual performance-based formula rate based on 2021 actual recoverable costs and expected net plant additions for 2022, an increase to include the 2021 revenue requirement reconciliation adjustment including a capital structure composed of 54% common equity, and a decrease for the conclusion of the 2020 revenue requirement reconciliation adjustment, which will be fully collected from customers in 2022, consistent with the ICC’s December 2021 annual update filing order. In August 2022, the ICC staff submitted its calculation of the revenue requirement included in Ameren Illinois’ update filing, recommending a $61 million increase in Ameren Illinois’ electric distribution service rates, which is based on a capital structure composed of 50% common equity. An ICC decision in this proceeding is required by December 2022, with new rates effective in January 2023. Electric Customer Energy-Efficiency Investments In June 2022, Ameren Illinois filed its annual electric customer energy-efficiency formula rate update to increase its rates by $17 million with the ICC. In August 2022, the ICC staff submitted a calculation of the revenue requirement included in Ameren Illinois’ filing, recommending a $15 million increase in rates. An ICC decision in this proceeding is required by December 2022, with new rates effective January 2023. In June 2022, the ICC issued an order approving Ameren Illinois’ revised energy-efficiency plan that includes annual investments in electric energy-efficiency programs of approximately $120 million per year through 2025, which reflects the increased level of annual investments allowed under the IETL. The ICC has the ability to reduce the amount of electric energy-efficiency savings goals in future program years if there are insufficient cost-effective programs available, which could reduce the investments in electric energy-efficiency programs. The electric energy-efficiency program investments and the return on those investments are collected from customers through a rider and are not recovered through the electric distribution service performance-based formula ratemaking framework. Illinois Senate Bill 3866 In May 2022, Illinois Senate Bill 3866 was enacted and became effective. This legislation makes certain amendments to the IETL, including amendments to increase the level of funding for the Energy Transition Assistance Fund. As a result of this legislation, Ameren Illinois expects to collect up to $50 million annually related to this fund, beginning in January 2023. Funds collected by Ameren Illinois will be remitted in the month following collection to an Illinois state agency, with no impact to results of operations. RTO Cost-Benefit Study In July 2022, an Illinois law prohibiting the state’s oversight of certain electric utilities’ choice of RTO membership ceased to be effective. Given the change in law and the high prices resulting from MISO’s April 2022 capacity auction, the ICC issued an order requiring Ameren Illinois to perform a cost-benefit study of continued participation in the MISO compared to participation in PJM Interconnection LLC, another RTO. The cost-benefit study will examine the impacts of participation in each RTO, including reliability, resiliency, affordability, and environmental impacts, among other things, for a period of five to 10 years beginning June 2024. The ICC order requires Ameren Illinois to file the study by July 2023. A 30-day comment period will follow. The ICC is under no obligation to issue an order related to the cost-benefit study. QIP Reconciliation Hearing In March 2020, Ameren Illinois filed its annual request with the ICC for a reconciliation hearing to determine the accuracy and prudence of natural gas capital investments recovered under the QIP rider during 2019. In August 2021, the Illinois Attorney General’s office challenged the recovery of capital investments that were made during 2019, alleging that the ICC should disallow approximately $70 million in natural gas capital investments as improper and imprudent, providing a potential over-recovery of approximately $3 million in 2019. In August and December 2021, the ICC staff filed testimony that supports the prudence and reasonableness of the capital investments made during 2019. Ameren Illinois’ 2019 QIP rate recovery request under review by the ICC is within the rate increase limitations allowed by law. The ICC is under no deadline to issue an order in this proceeding. Federal Transmission Formula Rate Revisions In February 2020, the MISO, on behalf of Ameren Missouri, Ameren Illinois, and ATXI, filed requests with the FERC to revise each company’s transmission formula rate calculations with respect to the calculation used for materials and supplies inventories included in rate base. In May 2020, the FERC issued orders approving the revisions prospectively. In addition, the FERC declined to order refunds for earlier periods, as requested by intervenors in Ameren Illinois’ filing, but directed its audit staff to review historical rate recovery in connection with an ongoing FERC audit. Separately, in March 2021, the FERC issued an order related to an intervenor challenge to Ameren Illinois’ 2020 transmission formula rate update. As a result of this order, in March 2021, Ameren Illinois recorded a regulatory liability of $9 million, largely as a reduction of electric operating revenues, to reflect expected refunds, including interest, primarily related to the historical rate recovery of materials and supplies inventories included in rate base. The refund amount was reflected in rates as of January 2022 and will be refunded to customers by the end of 2022. Ameren Missouri, Ameren Illinois, and ATXI filed appeals of the FERC’s May 2020 and March 2021 orders, and related FERC orders denying requests for rehearing, to the United States Court of Appeals for the District of Columbia Circuit. In January 2022, the appeals were consolidated by the court. The court is under no deadline to address the appeal. Regardless of the outcome of the appeal, the impact of the May 2020 and March 2021 orders is not expected to be material to Ameren’s, Ameren Missouri’s, or Ameren Illinois’ results of operations, financial position, or liquidity. FERC Complaint Cases Since November 2013, the allowed base ROE for FERC-regulated transmission rate base under the MISO tariff has been subject to customer complaint cases and has been changed by various FERC orders. In May 2020, the FERC issued an order, which set the allowed base ROE to 10.02%, and required refunds, with interest, for the periods November 2013 to February 2015 and from late September 2016 forward. Ameren and Ameren Illinois paid these refunds, including interest, by March 31, 2022. In June and July 2020, Ameren Missouri, Ameren Illinois, and ATXI, as well as various customers, petitioned the United States Court of Appeals for the District of Columbia Circuit for review of the May 2020 order, challenging certain aspects of the new ROE methodology established. The petition filed by Ameren Missouri, Ameren Illinois, and ATXI challenged the refunds required for the period from September 2016 to May 2020. In August 2022, the court issued a ruling that granted the customers’ petition for review, vacated the FERC’s previous MISO ROE-determining orders, and remanded the proceedings to the FERC. The currently allowed base ROE of 10.02% will remain effective for customer billings, but subject to refund if the base ROE is changed by the FERC in a future order. The FERC is under no deadline to issue an order related to these proceedings. A 50 basis point change in the FERC-allowed ROE would affect Ameren’s and Ameren Illinois’ annual revenue by an estimated $17 million and $11 million, respectively, based on each company’s 2022 projected rate base.

Short-Term Debt And Liquidity

9 Months Ended

Sep. 30, 2022

Debt Disclosure [Abstract]

SHORT-TERM DEBT AND LIQUIDITY

The liquidity needs of the Ameren Companies are typically supported through the use of available cash, drawings under committed credit agreements, commercial paper issuances, and, in the case of Ameren Missouri and Ameren Illinois, short-term affiliate borrowings. See Note 4 – Short-term Debt and Liquidity under Part II, Item 8, in the Form 10-K for a description of our indebtedness provisions and other covenants as well as a description of money pool arrangements.

Short-term Borrowings

The Missouri Credit Agreement and the Illinois Credit Agreement are available to support issuances under Ameren (parent)’s, Ameren Missouri’s, and Ameren Illinois’ commercial paper programs, respectively, subject to borrowing sublimits, and the issuance of letters of credit. As of September 30, 2022, based on commercial paper outstanding and letters of credit issued under the Credit Agreements, along with cash and cash equivalents, the net liquidity available to Ameren (parent), Ameren Missouri, and Ameren Illinois, collectively, was $1.1 billion. The Ameren Companies were in compliance with the covenants in their Credit Agreements as of September 30, 2022. As of September 30, 2022, the ratios of consolidated indebtedness to consolidated total capitalization, calculated in accordance with the provisions of the Credit Agreements, were 59%, 49%, and 45% for Ameren, Ameren Missouri, and Ameren Illinois, respectively.

The following table presents commercial paper outstanding, net of issuance discounts, as of September 30, 2022, and December 31, 2021. There were no borrowings outstanding under the Credit Agreements as of September 30, 2022, or December 31, 2021.


	September 30, 2022		December 31, 2021
Ameren (parent)	$	690	$	277
Ameren Missouri	178		165
Ameren Illinois	353		103
Ameren consolidated	$	1,221	$	545

The following table summarizes the activity and relevant interest rates for Ameren (parent)’s, Ameren Missouri’s, and Ameren Illinois’ commercial paper issuances and borrowings under the Credit Agreements in the aggregate for the nine months ended September 30, 2022 and 2021:


	Ameren (parent)			Ameren Missouri			Ameren Illinois			Ameren Consolidated
2022
Average daily amount outstanding	$	439		$	253		$	99		$	791

Weighted-average interest rate	1.58		%	1.16		%	1.77		%	1.47		%
Peak amount outstanding during period(a)	$	690		$	539		$	354		$	1,222
Peak interest rate	3.55		%	3.55		%	3.60		%	3.60		%
2021
Average daily amount outstanding	$	404		$	121		$	140		$	665

Weighted-average interest rate	0.23		%	0.22		%	0.22		%	0.22		%
Peak amount outstanding during period(a)	$	650		$	546		$	485		$	1,134
Peak interest rate	0.33		%	0.25		%	0.25		%	0.33		%

(a)The timing of peak outstanding commercial paper issuances and borrowings under the Credit Agreements varies by company. Therefore, the sum of individual company peak amounts may not equal the Ameren consolidated peak for the period.

Money Pools

Ameren has money pool agreements with and among its subsidiaries to coordinate and provide for certain short-term cash and working capital requirements. The average interest rate for borrowings under the utility money pool for the three and nine months ended September 30, 2022, was 2.48% and 1.29%, respectively (2021 – 0.06% and 0.17%, respectively). See Note 8 – Related-party Transactions for the amount of interest income and expense from the utility money pool arrangements recorded by Ameren Missouri and Ameren Illinois for the three and nine months ended September 30, 2022 and 2021.

Long-Term Debt And Equity Financings	9 Months Ended
Long-Term Debt And Equity Financings	Sep. 30, 2022
Long-Term Debt And Equity Financings [Abstract]
LONG-TERM DEBT AND EQUITY FINANCINGS	LONG-TERM DEBT AND EQUITY FINANCINGS Ameren For the three and nine months ended September 30, 2022, Ameren issued a total of 0.1 million and 0.4 million shares of common stock, respectively, under its DRPlus and 401(k) plan, and received proceeds of $4 million and $29 million, respectively, and had a receivable of $8 million as of September 30, 2022. In addition, in the first quarter of 2022, Ameren issued 0.4 million shares of common stock valued at $31 million upon the settlement of stock-based compensation awards. In May 2021, Ameren entered into an equity distribution sales agreement pursuant to which Ameren may offer and sell from time to time up to $750 million of its common stock through an ATM program, which includes the ability to enter into forward sales agreements. There were no shares issued under the ATM program for the three and nine months ended September 30, 2022. As of September 30, 2022, Ameren had substantially utilized the available capacity under the ATM program, which takes into account the forward sale agreements discussed below. Ameren has entered into multiple forward sale agreements under the ATM program with various counterparties relating to 6.6 million shares of common stock. Related to the forward sale agreements outstanding as of September 30, 2022, these agreements can be settled at Ameren’s discretion on or prior to dates ranging from May 3, 2023 to March 8, 2024. On a settlement date or dates, if Ameren elects to physically settle a forward sale agreement, Ameren will issue shares of common stock to the counterparties at the then-applicable forward sale price. The initial forward sale price for the agreements ranged from $86.35 to $94.80 with an average initial forward sale price of $90.31. Each initial forward sale price is subject to adjustment based on a floating interest rate factor equal to the overnight bank funding rate less a spread of 75 basis points, and will be subject to decrease on certain dates specified in the forward sale agreements by specified amounts related to expected dividends on shares of the common stock during the term of the forward sale agreements. If the overnight bank funding rate is less than the spread on any day, the interest rate factor will result in a reduction of the forward sale price. The forward sale agreements will be physically settled unless Ameren elects to settle in cash or to net share settle. At September 30, 2022, Ameren could have settled the forward sale agreements with physical delivery of 6.6 million shares of common stock to the respective counterparties in exchange for cash of $587 million. Alternatively, the forward sale agreements could have also been settled at September 30, 2022, with the counterparties delivering approximately $58 million of cash or approximately 0.7 million shares of common stock to Ameren. In connection to the forward sale agreements, the various counterparties, or their affiliates, borrowed from third parties and sold 6.6 million shares of common stock. The gross sales price of these shares totaled $600 million. In connection with such sales, the counterparties were deemed to have received commissions of $6 million. Ameren has not received any proceeds from such sales of borrowed shares. The forward sale agreements have been classified as equity transactions. Ameren Missouri In April 2022, Ameren Missouri issued $525 million of 3.90% first mortgage bonds due April 2052, with interest payable semiannually on April 1 and October 1 of each year, beginning October 1, 2022. Ameren Missouri received net proceeds of $519 million, which were used to repay short-term debt and for near-term capital expenditures. Ameren Missouri intends to allocate an amount equal to the proceeds, after expenses, to sustainability projects meeting certain eligibility criteria. Ameren Illinois In August 2022, Ameren Illinois issued $500 million of 3.85% first mortgage bonds due September 2032, with interest payable semiannually on March 1 and September 1 of each year, beginning March 1, 2023. Ameren Illinois received net proceeds of $496 million, which were used to repay $400 million principal amount of its 2.70% senior secured notes that matured in September 2022 and short-term debt. ATXI In November 2021, pursuant to a note purchase agreement, ATXI agreed to issue $95 million of its 2.96% senior unsecured notes due 2052, with interest payable semiannually on February 25 and August 25 of each year, beginning February 25, 2023, through a private placement offering exempt from registration under the Securities Act of 1933, as amended. In August 2022, ATXI issued the notes and received net proceeds of $95 million, which were used to refinance the remaining portion of an intercompany long-term note with Ameren (parent), repay $50 million in principal amount of its 3.43% senior unsecured notes in August 2022, and repay short-term debt. Indenture Provisions and Other Covenants See Note 5 – Long-term Debt and Equity Financings under Part II, Item 8, in the Form 10-K for a description of our indenture provisions and other covenants, as well as restrictions on the payment of dividends. At September 30, 2022, the Ameren Companies were in compliance with the provisions and covenants contained in their indentures and articles of incorporation, as applicable, and ATXI was in compliance with the provisions and covenants contained in its note purchase agreements. Off-balance-sheet Arrangements At September 30, 2022, none of the Ameren Companies had any significant off-balance-sheet financing arrangements, other than variable interest entities and the multiple forward sale agreements under the ATM program relating to common stock. See Note 1 – Summary of Significant Accounting Policies for further detail concerning variable interest entities.

Other Income, Net

9 Months Ended

Sep. 30, 2022

Other Nonoperating Income (Expense) [Abstract]

OTHER INCOME, NET

The following table presents the components of “Other Income, Net” in the Ameren Companies’ statements of income for the three and nine months ended September 30, 2022 and 2021:


	Three Months				Nine Months
	2022		2021		2022		2021
Ameren:

Allowance for equity funds used during construction	$	12	$	14	$	31	$	30
Interest income on industrial development revenue bonds	6		7		18		19


Non-service cost components of net periodic benefit income(a)	45		34		138		102
Miscellaneous income	5		1		14		7
Earnings (losses) related to equity method investments	(3)		2		1		8
Donations	(1)		(1)		(5)		(5)
Miscellaneous expense	(6)		(1)		(17)		(10)
Total Other Income, Net	$	58	$	56	$	180	$	151
Ameren Missouri:

Allowance for equity funds used during construction	$	7	$	7	$	17	$	17
Interest income on industrial development revenue bonds	6		7		18		19

Non-service cost components of net periodic benefit income(a)	13		13		41		41
Miscellaneous income	2		2		5		3
Donations	—		—		(2)		(1)
Miscellaneous expense	(3)		(2)		(7)		(5)
Total Other Income, Net	$	25	$	27	$	72	$	74
Ameren Illinois:

Allowance for equity funds used during construction	$	5	$	7	$	14	$	13


Non-service cost components of net periodic benefit income	21		13		63		41
Miscellaneous income	4		—		9		4
Donations	(1)		(1)		(3)		(4)
Miscellaneous expense	(3)		—		(8)		(5)
Total Other Income, Net	$	26	$	19	$	75	$	49

(a)For the three and nine months ended September 30, 2022, the non-service cost components of net periodic benefit income were adjusted by amounts deferred of $5 million and $16 million, respectively, due to a regulatory tracking mechanism for the difference between the level of such costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates. The deferral was $(3) million and $(6) million for both the three and nine months ended September 30, 2021, respectively. See Note 11– Retirement Benefits for additional information.

Derivative Financial Instruments

9 Months Ended

Sep. 30, 2022

Derivative Instruments and Hedging Activities Disclosure [Abstract]

DERIVATIVE FINANCIAL INSTRUMENTS

We use derivatives to manage the risk of changes in market prices for natural gas, power, and uranium, as well as the risk of changes in rail transportation surcharges through fuel oil hedges. Such price fluctuations may cause the following:

•an unrealized appreciation or depreciation of our contracted commitments to purchase or sell when purchase or sale prices under the commitments are compared with current commodity prices;

•market values of natural gas and uranium inventories that differ from the cost of those commodities in inventory;

•actual cash outlays for the purchase of these commodities that differ from anticipated cash outlays; and

•actual off-system sales revenues that differ from anticipated revenues.

The derivatives that we use to hedge these risks are governed by our risk management policies for forward contracts, futures, options, and swaps. Our net positions are continually assessed within our structured hedging programs to determine whether new or offsetting transactions are required. The goal of the hedging program is generally to mitigate financial risks while ensuring that sufficient volumes are available to meet our requirements. Contracts we enter into as part of our risk management program may be settled financially, settled by physical delivery, or net settled with the counterparty.

All contracts considered to be derivative instruments are required to be recorded on the balance sheet at their fair values, unless the NPNS exception applies. Many of our physical contracts, such as our purchased power contracts, qualify for the NPNS exception to derivative accounting rules. The revenue or expense on NPNS contracts is recognized at the contract price upon physical delivery. The following disclosures exclude NPNS contracts and other non-derivative commodity contracts that are accounted for under the accrual method of accounting.

If we determine that a contract meets the definition of a derivative and is not eligible for the NPNS exception, we review the contract to determine whether the resulting gains or losses qualify for regulatory deferral. Derivative contracts that qualify for regulatory deferral are recorded at fair value, with changes in fair value recorded as regulatory assets or liabilities in the period in which the change occurs. We believe derivative losses and gains deferred as regulatory assets and liabilities are probable of recovery, or refund, through future rates charged to customers. Regulatory assets and liabilities are amortized to operating income as related losses and gains are reflected in rates charged to customers. Therefore, gains and losses on these derivatives have no effect on operating income. As of September 30, 2022, and December 31, 2021, all contracts that met the definition of a derivative and were not eligible for the NPNS exception received regulatory deferral. Cash flows for all derivative financial instruments are classified in cash flows from operating activities.

The following table presents open gross commodity contract volumes by commodity type for derivative assets and liabilities as of September 30, 2022, and December 31, 2021. As of September 30, 2022, these contracts extended through October 2024, October 2027, May 2032 and March 2024 for fuel oils, natural gas, power and uranium, respectively:


	Quantity (in millions)
	September 30, 2022			December 31, 2021
Commodity	Ameren Missouri	Ameren Illinois	Ameren	Ameren Missouri	Ameren Illinois	Ameren
Fuel oils (in gallons)	19	—	19	30	—	30
Natural gas (in mmbtu)	43	144	187	35	144	179
Power (in MWhs)	2	6	8	6	6	12
Uranium (pounds in thousands)	406	—	406	586	—	586

The following table presents the carrying value and balance sheet location of all derivative commodity contracts, none of which were designated as hedging instruments, as of September 30, 2022, and December 31, 2021:


			September 30, 2022					December 31, 2021
	Balance Sheet Location		Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren







Fuel oils	Other current assets		12		—		12			8		—		8
	Other assets		3		—		3			5		—		5
Natural gas	Mark-to-market derivative assets		(a)		57		(a)			(a)		28		(a)

	Other current assets		14		—		71			7		—		35
	Other assets		13		21		34			5		13		18
Power	Mark-to-market derivative assets		(a)		11		(a)			(a)		—		(a)

	Other current assets		28		—		39			23		—		23
	Other assets		—		5		5			—		—		—


Uranium	Other current assets		2		—		2			—		—		—
	Other assets		1		—		1			1		—		1
	Total assets	$	73	$	94	$	167		$	49	$	41	$	90



Fuel oils	Other deferred credits and liabilities		1		—		1			—		—		—
Natural gas	Mark-to-market derivative liabilities		2		(a)		(a)			2		(a)		(a)

	Other current liabilities		—		9		11			—		6		8
	Other deferred credits and liabilities		1		3		4			1		2		3
Power	Mark-to-market derivative liabilities		111		(a)		(a)			50		(a)		(a)

	Other current liabilities		—		—		111			—		9		59
	Other deferred credits and liabilities		14		36		50			23		108		131
Uranium	Mark-to-market derivative liabilities		—		(a)		(a)			1		(a)		(a)

	Other current liabilities		—		—		—			—		—		1

	Total liabilities	$	129	$	48	$	177		$	77	$	125	$	202

(a)Balance sheet line item not applicable to registrant.

We believe that entering into master netting arrangements or similar agreements mitigates the level of financial loss that could result from default by allowing net settlement of derivative assets and liabilities. These master netting arrangements allow the counterparties to net settle sale and purchase transactions. Further, collateral requirements are calculated at the master netting arrangement or similar agreement level by counterparty.

The following table provides the recognized gross derivative balances and the net amounts of those derivatives subject to an enforceable master netting arrangement or similar agreement as of September 30, 2022, and December 31, 2021:


			Gross Amounts Not Offset in the Balance Sheet
Commodity Contracts Eligible to be Offset	Gross Amounts Recognized in the Balance Sheet		Derivative Instruments		Cash Collateral Received/Posted(a)		Net Amount
September 30, 2022
Assets:
Ameren Missouri	$	73	$	18	$	2	$	53
Ameren Illinois	94		13		1		80
Ameren	$	167	$	31	$	3	$	133
Liabilities:
Ameren Missouri	$	129	$	18	$	99	$	12
Ameren Illinois	48		13		—		35
Ameren	$	177	$	31	$	99	$	47
December 31, 2021
Assets:
Ameren Missouri	$	49	$	15	$	—	$	34
Ameren Illinois	41		4		—		37
Ameren	$	90	$	19	$	—	$	71
Liabilities:
Ameren Missouri	$	77	$	15	$	47	$	15
Ameren Illinois	125		4		—		121
Ameren	$	202	$	19	$	47	$	136

(a)Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Current collateral assets” and “Other assets” on the balance sheet for Ameren and Ameren Missouri and “Other current assets” and “Other assets” for Ameren Illinois.

Credit Risk

In determining our concentrations of credit risk related to derivative instruments, we review our individual counterparties and categorize each counterparty into groupings according to the primary business in which each engages. As of September 30, 2022, if counterparty groups were to fail completely to perform on contracts, Ameren, Ameren Missouri, and Ameren Illinois’ maximum exposure related to derivative assets, predominantly from financial institutions, was $142 million, $55 million, and $87 million, respectively. The potential loss on counterparty exposures may be reduced or eliminated by the application of master netting arrangements or similar agreements and collateral held. As of September 30, 2022, the potential loss after consideration of the application of master netting arrangements or similar agreements and collateral held for Ameren, Ameren Missouri, and Ameren Illinois was $124 million, $43 million, and $81 million, respectively.

Certain of our derivative instruments contain collateral provisions tied to the Ameren Companies’ credit ratings. If our credit ratings were downgraded below investment grade, or if a counterparty with reasonable grounds for uncertainty regarding our ability to satisfy an obligation requested adequate assurance of performance, additional collateral postings might be required. The additional collateral required is the net liability position allowed under master netting arrangements or similar agreements, assuming (1) the credit risk-related contingent features underlying these arrangements were triggered and (2) those counterparties with rights to do so requested collateral. As of September 30, 2022, the aggregate fair value of derivative instruments with credit risk-related contingent features in a gross liability position, the cash collateral posted, and the aggregate amount of additional collateral that counterparties could require were each immaterial to Ameren, Ameren Missouri, and Ameren Illinois.

Fair Value Measurements

9 Months Ended

Sep. 30, 2022

Fair Value Disclosures [Abstract]

Fair Value Disclosures

FAIR VALUE MEASUREMENTS

Fair value is defined as the price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Fair value measurements are classified in three levels based on the fair value hierarchy as defined by GAAP. See Note 8 – Fair Value Measurements under Part II, Item 8, of the Form 10-K for information related to hierarchy levels and valuation techniques.

We consider nonperformance risk in our valuation of derivative instruments by analyzing our own credit standing and the credit standing of our counterparties, and by considering any credit enhancements (e.g., collateral). Included in our valuation, and based on current market conditions, is a valuation adjustment for counterparty default derived from market data such as the price of credit default swaps, bond yields, and credit ratings. No material gains or losses related to valuation adjustments for counterparty default risk were recorded at Ameren, Ameren Missouri, or Ameren Illinois in the three and nine months ended September 30, 2022 or 2021. At September 30, 2022, and

December 31, 2021, the counterparty default risk valuation adjustment related to derivative contracts was immaterial for Ameren, Ameren Missouri, and Ameren Illinois.

The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of September 30, 2022, and December 31, 2021:


		September 30, 2022									December 31, 2021
		Level 1		Level 2		Level 3		Total			Level 1		Level 2		Level 3		Total
Assets:
Ameren Missouri
	Derivative assets – commodity contracts:
	Fuel oils	$	13	$	—	$	2	$	15		$	13	$	—	$	—	$	13
	Natural gas	1		26		—		27			—		12		—		12
	Power	9		—		19		28			10		—		13		23
	Uranium	—		—		3		3			—		—		1		1
	Total derivative assets – commodity contracts	$	23	$	26	$	24	$	73		$	23	$	12	$	14	$	49
	Nuclear decommissioning trust fund:

	Equity securities:
	U.S. large capitalization	$	574	$	—	$	—	$	574		$	824	$	—	$	—	$	824
	Debt securities:
	U.S. Treasury and agency securities	—		148		—		148			—		141		—		141
	Corporate bonds	—		115		—		115			—		131		—		131


	Other	—		64		—		64			—		56		—		56
	Total nuclear decommissioning trust fund	$	574	$	327	$	—	$	901	(a)	$	824	$	328	$	—	$	1,152	(a)
	Total Ameren Missouri	$	597	$	353	$	24	$	974		$	847	$	340	$	14	$	1,201
Ameren Illinois
	Derivative assets – commodity contracts:
	Natural gas	$	6	$	65	$	7	$	78		$	1	$	33	$	7	$	41
	Power	—		—		16		16			—		—		—		—
	Total Ameren Illinois	$	6	$	65	$	23	$	94		$	1	$	33	$	7	$	41
Ameren
	Derivative assets – commodity contracts(b)	$	29	$	91	$	47	$	167		$	24	$	45	$	21	$	90
	Nuclear decommissioning trust fund(c)	574		327		—		901		(a)	824		328		—		1,152		(a)
	Total Ameren	$	603	$	418	$	47	$	1,068		$	848	$	373	$	21	$	1,242
Liabilities:
Ameren Missouri
	Derivative liabilities – commodity contracts:
	Fuel oils	$	1	$	—	$	—	$	1		$	—	$	—	$	—	$	—
	Natural gas	—		2		1		3			—		2		1		3
	Power	98		—		27		125			45		—		28		73
	Uranium	—		—		—		—			—		—		1		1
	Total Ameren Missouri	$	99	$	2	$	28	$	129		$	45	$	2	$	30	$	77
Ameren Illinois
	Derivative liabilities – commodity contracts:
	Natural gas	$	—	$	6	$	6	$	12		$	—	$	5	$	3	$	8
	Power	—		—		36		36			—		—		117		117
	Total Ameren Illinois	$	—	$	6	$	42	$	48		$	—	$	5	$	120	$	125
Ameren
	Derivative liabilities – commodity contracts(b)	$	99	$	8	$	70	$	177		$	45	$	7	$	150	$	202

(a)Balance excludes $9 million and $7 million of cash and cash equivalents, receivables, payables, and accrued income, net, for September 30, 2022, and December 31, 2021, respectively.

(b)See the Ameren Missouri and Ameren Illinois sections of the table for a breakout of the fair value of Ameren’s derivative assets and liabilities by type of commodity.

(c)See the Ameren Missouri section of the table for a breakout of the fair value of Ameren’s nuclear decommissioning trust fund by investment type.

Level 3 fuel oils, natural gas, and uranium derivative contract assets and liabilities measured at fair value on a recurring basis were immaterial for all periods presented. The following table presents the fair value reconciliation of Level 3 power derivative contract assets and liabilities measured at fair value on a recurring basis for the three and nine months ended September 30, 2022 and 2021:


	2022						2021
	Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren
For the three months ended September 30:
Beginning balance at July 1	$	(36)	$	(44)	$	(80)		$	(5)	$	(166)	$	(171)
Realized and unrealized gains/(losses) included in regulatory assets/liabilities	(10)		30		20			(16)		19		3


Settlements	38		(6)		32			(2)		3		1


Ending balance at September 30	$	(8)	$	(20)	$	(28)		$	(23)	$	(144)	$	(167)
Change in unrealized gains/(losses) related to assets/liabilities held at September 30	$	(3)	$	28	$	25		$	(17)	$	19	$	2
For the nine months ended September 30:
Beginning balance at January 1	$	(15)	$	(117)	$	(132)		$	2	$	(198)	$	(196)
Realized and unrealized gains/(losses) included in regulatory assets/liabilities	(56)		105		49			(22)		43		21


Settlements	63		(8)		55			(3)		11		8


Ending balance at September 30	$	(8)	$	(20)	$	(28)		$	(23)	$	(144)	$	(167)
Change in unrealized gains/(losses) related to assets/liabilities held at September 30	$	(39)	$	100	$	61		$	(21)	$	42	$	21

All gains or losses related to our Level 3 derivative commodity contracts are expected to be recovered or returned through customer rates; therefore, there is no impact to either net income or other comprehensive income resulting from changes in the fair value of these instruments.

The following table describes the valuation techniques and significant unobservable inputs utilized for the fair value of our Level 3 power derivative contract assets and liabilities as of September 30, 2022, and December 31, 2021:


			Fair Value						Weighted Average(b)
	Commodity		Assets		Liabilities	Valuation Technique(s)	Unobservable Input(a)	Range









2022	Power(c)	$	35	$	(63)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps ($/MWh)	42 – 118	60

							Nodal basis ($/MWh)	(15) – 2	(5)


							Trend rate (%)	0 – 1	0








































2021	Power(d)	$	13	$	(145)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps ($/MWh)	32 – 55	40

							Nodal basis ($/MWh)	(14) – 0	(2)


							Trend rate (%)	(e)	0

(a)Generally, significant increases (decreases) in these inputs in isolation would result in a significantly higher (lower) fair value measurement.

(b)Unobservable inputs were weighted by relative fair value.

(c)Valuations through 2031 use visible forward prices adjusted for nodal-to-hub basis differentials. Valuations beyond 2031 use a trend rate factor and are similarly adjusted for nodal-to-hub basis differentials.

(d)Valuations through 2029 use visible forward prices adjusted for nodal-to-hub basis differentials. Valuations beyond 2029 use a trend rate factor and are similarly adjusted for nodal-to-hub basis differentials.

(e)No meaningful range around weighted average.

The following table sets forth the carrying amount and, by level within the fair value hierarchy, the fair value of financial assets and liabilities disclosed, but not recorded, at fair value as of September 30, 2022, and December 31, 2021:


	Carrying Amount			Fair Value
				Level 1		Level 2		Level 3			Total
	September 30, 2022
Ameren:
Cash, cash equivalents, and restricted cash	$	180		$	180	$	—	$	—		$	180
Investments in industrial development revenue bonds(a)	248			—		248		—			248
Short-term debt	1,221			—		1,221		—			1,221
Long-term debt (including current portion)(a)	13,732		(b)	—		11,493		446		(c)	11,939
Ameren Missouri:
Cash, cash equivalents, and restricted cash	$	7		$	7	$	—	$	—		$	7

Investments in industrial development revenue bonds(a)	248			—		248		—			248
Short-term debt	178			—		178		—			178

Long-term debt (including current portion)(a)	6,140		(b)	—		5,352		—			5,352
Ameren Illinois:
Cash, cash equivalents, and restricted cash	$	166		$	166	$	—	$	—		$	166

Short-term debt	353			—		353		—			353

Long-term debt (including current portion)	4,489		(b)	—		3,868		—			3,868
	December 31, 2021
Ameren:
Cash, cash equivalents, and restricted cash	$	155		$	155	$	—	$	—		$	155
Investments in industrial development revenue bonds(a)	248			—		248		—			248
Short-term debt	545			—		545		—			545
Long-term debt (including current portion)(a)	13,067		(b)	—		13,930		591		(c)	14,521
Ameren Missouri:
Cash, cash equivalents, and restricted cash	$	8		$	8	$	—	$	—		$	8

Investments in industrial development revenue bonds(a)	248			—		248		—			248
Short-term debt	165			—		165		—			165
Long-term debt (including current portion)(a)	5,619		(b)	—		6,321		—			6,321
Ameren Illinois:
Cash, cash equivalents, and restricted cash	$	133		$	133	$	—	$	—		$	133
Short-term debt	103			—		103		—			103

Long-term debt (including current portion)	4,392		(b)	—		4,971		—			4,971

(a)Ameren and Ameren Missouri have investments in industrial development revenue bonds, classified as held-to-maturity and recorded in “Other Assets,” that are equal to the finance obligations for the Peno Creek and Audrain CT energy centers. As of September 30, 2022, and December 31, 2021, the carrying amount of both the investments in industrial development revenue bonds and the finance obligations approximated fair value.

(b)Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $99 million, $42 million, and $41 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of September 30, 2022. Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $94 million, $38 million, and $39 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of December 31, 2021.

(c)The Level 3 fair value amount consists of ATXI’s senior unsecured notes.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Related Party Transactions

9 Months Ended

Sep. 30, 2022

RELATED PARTY TRANSACTIONS

RELATED-PARTY TRANSACTIONS

In the ordinary course of business, Ameren Missouri and Ameren Illinois have engaged in, and may in the future engage in, affiliate transactions. These transactions primarily consist of natural gas and power purchases and sales, services received or rendered, and borrowings and lendings. Transactions between Ameren’s subsidiaries are reported as affiliate transactions on their individual financial statements, but those transactions are eliminated in consolidation for Ameren’s consolidated financial statements. For a discussion of material related-party agreements and money pool arrangements, see Note 13 – Related-party Transactions and Note 4 – Short-term Debt and Liquidity under Part II, Item 8, of the Form 10-K.

Support Services Agreements

Ameren Missouri and Ameren Illinois had long-term receivables included in “Other assets” from Ameren Services of $80 million and $83 million, respectively, as of September 30, 2022, and $77 million and $80 million, respectively, as of December 31, 2021, related to Ameren Services’ allocated portion of Ameren’s pension and postretirement benefit plans.

Tax Allocation Agreement

See Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of the Form 10-K for a discussion of the tax allocation agreement. The following table presents the affiliate balances related to income taxes for Ameren Missouri and Ameren Illinois as of September 30, 2022, and December 31, 2021:


	September 30, 2022				December 31, 2021
	Ameren Missouri		Ameren Illinois		Ameren Missouri		Ameren Illinois
Income taxes payable to parent(a)	$	—	$	72	$	—	$	8
Income taxes receivable from parent(b)	12		—		27		18

(a)Included in “Accounts payable – affiliates” on the balance sheet.

(b)Included in “Accounts receivable – affiliates” on the balance sheet.

Effects of Related-party Transactions on the Statement of Income

The following table presents the impact on Ameren Missouri and Ameren Illinois of related-party transactions for the three and nine months ended September 30, 2022 and 2021:


				Three Months				Nine Months
Agreement	Income Statement Line Item			Ameren Missouri		Ameren Illinois		Ameren Missouri		Ameren Illinois
Ameren Missouri power supply	Operating Revenues	2022	$	2	$	(a)	$	7	$	(a)
agreements with Ameren Illinois		2021		5		(a)		10		(a)
Ameren Missouri and Ameren Illinois	Operating Revenues	2022	$	6	$	(b)	$	18	$	(b)
rent and facility services		2021		6		(b)		20		(b)
Ameren Missouri and Ameren Illinois miscellaneous	Operating Revenues	2022	$	(b)	$	(b)	$	(b)	$	1
services		2021		(b)		3		(b)		5
Total Operating Revenues		2022	$	8	$	(b)	$	25	$	1
		2021		11		3		30		5
Ameren Illinois power supply	Purchased Power	2022	$	(a)	$	2	$	(a)	$	7
agreements with Ameren Missouri		2021		(a)		5		(a)		10
Ameren Missouri and Ameren Illinois	Purchased Power	2022	$	1	$	(b)	$	1	$	(b)
transmission services from ATXI		2021		1		(b)		3		1
Total Purchased Power		2022	$	1	$	2	$	1	$	7
		2021		1		5		3		11
Ameren Missouri and Ameren Illinois	Other Operations and Maintenance	2022	$	(b)	$	1	$	(b)	$	2
rent and facility services		2021		(b)		1		(b)		3
Ameren Services support services	Other Operations and Maintenance	2022	$	38	$	36	$	109	$	103
agreement		2021		41		37		110		101
Total Other Operations and		2022	$	38	$	37	$	109	$	105
Maintenance		2021		41		38		110		104
Money pool borrowings (advances)	(Interest Charges)/Other Income, Net	2022	$	(b)	$	(b)	$	(b)	$	(b)
		2021		(b)		(b)		(b)		(b)

(a)Not applicable.

(b)Amount less than $1 million.

Commitments And Contingencies	9 Months Ended
Commitments And Contingencies	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES We are involved in legal, tax, and regulatory proceedings before various courts, regulatory commissions, authorities, and governmental agencies with respect to matters that arise in the ordinary course of business, some of which involve substantial amounts of money. We believe that the final disposition of these proceedings, except as otherwise disclosed in the notes to our financial statements in this report and in the Form 10-K, will not have a material adverse effect on our results of operations, financial position, or liquidity. Reference is made to Note 1 – Summary of Significant Accounting Policies, Note 2 – Rate and Regulatory Matters, Note 9 – Callaway Energy Center, Note 13 – Related-party Transactions, and Note 14 – Commitments and Contingencies under Part II, Item 8, of the Form 10-K. See also Note 1 – Summary of Significant Accounting Policies, Note 2 – Rate and Regulatory Matters, Note 8 – Related-party Transactions, and Note 10 – Callaway Energy Center of this report. Environmental Matters Our electric generation, transmission, and distribution and natural gas distribution and storage operations must comply with a variety of statutes and regulations relating to the protection of the environment and human health and safety, including permitting programs implemented via federal, state, and local authorities. Such environmental laws address air emissions; discharges to water bodies; the storage, handling and disposal of hazardous substances and waste materials; siting and land use requirements; and potential ecological impacts. Complex and lengthy processes are required to obtain and renew approvals, permits, and licenses for new, existing, or modified facilities. Additionally, the use and handling of various chemicals or hazardous materials require release prevention plans and emergency response procedures. We employ dedicated personnel knowledgeable in environmental matters to oversee our business activities’ compliance with regulatory requirements. Environmental regulations have a significant impact on the electric utility industry and compliance with these regulations could be costly for Ameren Missouri, which operates coal-fired power plants. Regulations under the Clean Air Act that apply to the electric utility industry include the NSPS, the CSAPR, the MATS, and the National Ambient Air Quality Standards, which are subject to periodic review for certain pollutants. Collectively, these regulations cover a variety of pollutants, such as SO2, particulate matter, NOx, mercury, toxic metals and acid gases, and CO2 emissions from new power plants. Regulations implementing the Clean Water Act govern both intake and discharges of water, as well as evaluation of the ecological and biological impact of our operations and could require modifications to water intake structures or more stringent limitations on wastewater discharges. Depending upon the scope of modifications ultimately required by state regulators, capital expenditures associated with these modifications could be significant. The management and disposal of coal ash is regulated under the Resource Conservation and Recovery Act and the CCR Rule, which require the closure of certain surface impoundments at Ameren Missouri’s coal-fired energy centers. The individual or combined effects of compliance with existing and new environmental regulations could result in significant capital expenditures, increased operating costs, or the closure or alteration of operations at some of Ameren Missouri’s energy centers. Ameren and Ameren Missouri expect that such compliance costs would be recoverable through rates, subject to MoPSC prudence review, but the timing of costs and their recovery could be subject to regulatory lag. Additionally, Ameren Missouri’s wind generation facilities may be subject to operating restrictions to limit the impact on protected species. Nighttime operating restrictions may be required during the critical biological season, which typically occurs from April through October. Seasonal nighttime curtailment began at the High Prairie Renewable Energy Center at the end of March 2022. Ameren Missouri expects to resume nighttime operations in November 2022, but the extent and duration of future seasonal nighttime curtailment is unknown as assessment of mitigation technologies is ongoing. Ameren Missouri does not anticipate these operating curtailments to result in significant impacts on its results of operations, financial position, or liquidity. Ameren and Ameren Missouri estimate that they will need to make capital expenditures of $125 million to $175 million from 2022 through 2026 in order to comply with existing environmental regulations. Additional environmental controls beyond 2026 could be required. This estimate of capital expenditures includes ash pond closure and corrective action measures required by the CCR Rule and potential modifications to cooling water intake structures at existing power plants under Clean Water Act rules, all of which are discussed below. In addition to planned retirements of fossil fuel-fired energy centers as set forth in the 2022 Change to the 2020 IRP filed with the MoPSC in June 2022 and as noted in the NSR and Clean Air Act litigation and Illinois emissions standards discussed below, Ameren Missouri’s current plan for compliance with existing air emission regulations includes burning low-sulfur coal and installing new or optimizing existing air pollution control equipment. The actual amount of capital expenditures required to comply with existing environmental regulations may vary substantially from the above estimates because of uncertainty as to future permitting requirements made by state regulators and the EPA, potential revisions to regulatory obligations, and the cost of potential compliance strategies, among other things. The following sections describe the more significant environmental laws and rules and environmental enforcement and remediation matters that affect or could affect our operations. The EPA has initiated an administrative review of several regulations and proposed amendments to regulations and guidelines, including the CSAPR, which could ultimately result in the revision of all or part of such rules. Clean Air Act Federal and state laws, including CSAPR, regulate emissions of SO2 and NOx through the reduction of emissions at their source and the use and retirement of emission allowances. CSAPR is implemented through a series of phases, and the second phase became effective in 2017. In April 2022, the EPA proposed plans for additional emission reductions from power plants in Missouri, Illinois, and other states through revisions to the CSAPR; and additional emission reduction requirements may apply in subsequent years. The EPA expects to issue a final rule in March 2023. Ameren Missouri complies with current CSAPR requirements by minimizing emissions through the use of low-sulfur coal, operation of two scrubbers at its Sioux Energy Center, and optimization of other existing air pollution control equipment. Ameren Missouri could incur additional costs to lower its emissions at one or more of its energy centers to comply with additional CSAPR requirements in future years. These additional costs for compliance are expected to be recovered from customers through the FAC or higher base rates. CO2 Emissions Standards In June 2022, the United States Supreme Court issued its decision in West Virginia v. EPA. The decision clarifies that there are limits on how the EPA may regulate greenhouse gases absent further direction from the United States Congress. The court concluded that emission caps that would cause generation shifting from fossil-fuel-fired power plants to renewable energy facilities would require specific congressional authorization and that such authorization had not been given under the Clean Air Act. The decision by the United States Supreme Court may affect the EPA’s development of any new regulations to address CO2 emissions from coal- and natural gas-fired power plants; however, at this time, Ameren Missouri cannot predict the impact of any such regulations or the decision by the United States Supreme Court on the results of operations, financial position, and liquidity of Ameren or Ameren Missouri. NSR and Clean Air Act Litigation In January 2011, the United States Department of Justice, on behalf of the EPA, filed a complaint against Ameren Missouri in the United States District Court for the Eastern District of Missouri alleging that projects performed in 2007 and 2010 at the coal-fired Rush Island Energy Center violated provisions of the Clean Air Act and Missouri law. In January 2017, the district court issued a liability ruling against Ameren Missouri and, in September 2019, entered a remedy order that required Ameren Missouri to install a flue gas desulfurization system at the Rush Island Energy Center and a dry sorbent injection system at the Labadie Energy Center. Following an appeal from Ameren Missouri in August 2021, the United States Court of Appeals for the Eighth Circuit affirmed the liability ruling and the district court’s remedy order as it related to the installation of a flue gas desulfurization system at the Rush Island Energy Center, but reversed the order as it related to the installation of a dry sorbent injection system at the Labadie Energy Center. In November 2021, the court of appeals issued an order denying requests for consideration previously sought by both Ameren Missouri and the United States Department of Justice. Based on its assessment of available legal, operational, and regulatory alternatives, Ameren Missouri filed a motion in December 2021, with the district court to modify the remedy order to allow the retirement of the Rush Island Energy Center in advance of its previously expected useful life in lieu of installing a flue gas desulfurization system. The March 31, 2024 compliance date contained in the district court’s September 2019 remedy order remains in effect unless extended by the district court. In July 2022, in response to an Ameren Missouri request for a final, binding reliability assessment, the MISO designated the Rush Island Energy Center as a system support resource and concluded that certain mitigation measures, including transmission upgrades, should occur before the energy center is retired. The transmission upgrade projects have been approved by the MISO, and Ameren Missouri has started design and procurement activities necessary to complete the upgrades and expects to complete the upgrades by late 2025. In October 2022, the FERC approved a system support resource agreement, which became effective retroactively as of September 1, 2022. The agreement details the manner of continued operation for a system support resource that results in operating during peak demand times and emergencies. The system support resource designation and the related agreement are subject to annual renewal and revision. In September 2022, the Rush Island Energy Center began operating consistent with the system support resource agreement. In addition, in October 2022, the FERC established hearing and settlement procedures in response to an August 2022 request from Ameren Missouri for recovery of non-energy costs under the related MISO tariff. The FERC is under no deadline to issue an order related to this proceeding. Revenues and costs under the MISO tariff are expected to be included in the FAC. The district court has the authority to determine the retirement date and operating parameters for the Rush Island Energy Center and is not bound by the MISO determination of the Rush Island Energy Center as a system support resource or the FERC’s approval. The district court is under no deadline to issue a ruling modifying the remedy order. Related to this matter, in February 2022, the MoPSC issued an order directing the MoPSC staff to review the planned accelerated retirement of the Rush Island Energy Center. See Note 2 – Rate and Regulatory Matters for additional information. In connection with the planned accelerated retirement of the Rush Island Energy Center, Ameren Missouri expects to seek approval from the MoPSC to finance the costs associated with the retirement, including the remaining unrecovered net plant balance associated with the facility, through the issuance of securitized utility tariff bonds pursuant to the Missouri securitization statute. As such, Ameren Missouri did not request a change in the depreciation rates related to the Rush Island Energy Center in the electric regulatory rate review filed in August 2022. See Note 2 – Rate and Regulatory Matters for additional information on the August 2022 electric regulatory rate review. As of September 30, 2022, the Rush Island Energy Center had a net plant balance of approximately $0.6 billion included in plant to be abandoned, net, within “Property, Plant, and Equipment, Net” and a rate base of approximately $0.5 billion. See Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of the Form 10-K for additional information regarding plant to be abandoned, net. In addition, Ameren Missouri filed a 2022 Change to the 2020 IRP with the MoPSC in June 2022 to reflect, among other things, the planned acceleration of the retirement of the Rush Island Energy Center from 2039, the retirement year for the facility as reflected in the 2020 IRP and reflected in depreciation rates approved by the December 2021 MoPSC electric rate order. Ameren Missouri is unable to predict the ultimate resolution of this matter; however, such resolution could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. Clean Water Act The EPA’s regulations implementing Section 316(b) of the Clean Water Act require power plant operators to evaluate cooling water intake structures and identify measures for reducing the number of aquatic organisms impinged on a power plant’s cooling water intake screens or entrained through the plant’s cooling water system. All of Ameren Missouri’s coal-fired and nuclear energy centers are subject to the cooling water intake structures rule. Requirements of the rule are implemented by state regulators through the permit renewal process of each power plant’s water discharge permit. Permits for Ameren Missouri’s coal-fired and nuclear energy centers have been issued or are in the process of renewal. In 2015, the EPA issued a rule to revise the effluent limitation guidelines applicable to steam electric generating units. These guidelines established national standards for water discharges, prohibit effluent discharges of certain waste streams, and impose more stringent limitations on certain water discharges from power plants by 2025. To meet the requirements of the guidelines, Ameren Missouri installed dry ash handling systems and in 2020 completed construction of wastewater treatment facilities at three of its four coal-fired energy centers. The Meramec Energy Center will be retired by the end of 2022 and, as a result, does not require new wastewater and dry ash handling systems. CCR Management The EPA’s CCR Rule establishes requirements for the management and disposal of CCR from coal-fired power plants and will result in the closure of certain surface impoundments at Ameren Missouri’s energy centers. Ameren Missouri completed the closure of all surface impoundments at its Labadie and Rush Island energy centers in 2021, and has made significant progress by closing several surface impoundments at its Sioux and Meramec energy centers. Ameren Missouri plans to complete the closures of the remaining surface impoundments as required by the CCR Rule in 2024. In January 2022, Ameren Missouri received notices of a proposed determination by the EPA preliminarily denying Ameren Missouri’s requests to extend the timeline for operating certain surface impoundments located at the Sioux and Meramec energy centers. Pursuant to the terms of the proposed determinations, compliance with the CCR Rule’s requirements for closure of the surface impoundments would be required 135 days after the EPA issues a final determination. In February 2022, Ameren Missouri filed comments with the EPA requesting additional time to construct a CCR Rule-compliant impoundment at the Sioux Energy Center and complete the closure of the surface impoundments at the Meramec Energy Center. The EPA is under no deadline to issue a final determination. Continued use of surface impoundments at the Sioux or Meramec energy centers is necessary to support ongoing operations. Ameren Missouri will retire the Meramec Energy Center by the end of 2022, and construction of a CCR Rule-compliant surface impoundment at the Sioux Energy Center is expected to be completed by the end of 2022 to allow for continued operations. Ameren Missouri does not expect that this matter will have a material adverse effect on its results of operations, financial position, or liquidity. Ameren and Ameren Missouri have AROs of $49 million recorded on their respective balance sheets as of September 30, 2022, associated with CCR storage facilities. Ameren Missouri estimates it will need to make capital expenditures of $60 million to $80 million from 2022 through 2026 to implement its CCR management compliance plan, which includes installation of groundwater monitoring equipment and groundwater treatment facilities. Remediation The Ameren Companies are involved in a number of remediation actions to clean up sites impacted by the use or disposal of materials containing hazardous substances. Federal and state laws can require responsible parties to fund remediation regardless of their degree of fault, the legality of original disposal, or the ownership of a disposal site. As of September 30, 2022, Ameren Illinois has remediated the majority of the 44 former MGP sites in Illinois and could substantially conclude remediation efforts at the remaining sites by 2023. The ICC allows Ameren Illinois to recover such remediation and related litigation costs from its electric and natural gas utility customers through environmental cost riders that are subject to annual prudence reviews by the ICC. As of September 30, 2022, Ameren Illinois estimated the remaining obligation related to these former MGP sites at $71 million to $145 million. Ameren and Ameren Illinois recorded a liability of $71 million to represent the estimated minimum obligation for these sites, as no other amount within the range was a better estimate. About half of the remaining liability recorded relates to remediation activities that are expected to be completed after 2023. The scope of the remediation activities at these former MGP sites may increase as remediation efforts continue. Considerable uncertainty remains in these estimates because many site-specific factors can influence the actual costs, including unanticipated underground structures, the degree to which groundwater is encountered, regulatory changes, local ordinances, and site accessibility. The actual costs and timing of completion may vary substantially from these estimates. Our operations or those of our predecessor companies involve the use of, disposal of, and, in appropriate circumstances, the cleanup of substances regulated under environmental laws. We are unable to determine whether such historical practices will result in future environmental commitments or will affect our results of operations, financial position, or liquidity. Illinois Emission Standards The IETL established emission standards that became effective in September 2021. Ameren Missouri’s natural gas-fired energy centers in Illinois are subject to limits on emissions, including CO2 and NOx, equal to their unit-specific average emissions from 2018 through 2020, for any rolling twelve-month period beginning October 1, 2021, through 2029. Further reductions to emissions limits will become effective between 2030 and 2040, resulting in the closure of the Venice Energy Center by 2029. The reductions could also limit the operations of Ameren Missouri’s other four natural gas-fired energy centers located in the state of Illinois, and will result in their closure by 2040. These energy centers are utilized to support peak loads. Subject to conditions in the IETL, these energy centers may be allowed to exceed the emissions limits in order to maintain reliability of electric utility service as necessary. Ameren Missouri filed a 2022 Change to the 2020 IRP with the MoPSC in June 2022 to reflect, among other things, the updated scheduled retirement dates of the natural gas-fired energy centers located in the state of Illinois.

Callaway Energy Center

9 Months Ended

Sep. 30, 2022

Nuclear Waste Matters [Abstract]

CALLAWAY ENERGY CENTER

See Note 9 – Callaway Energy Center under Part II, Item 8, of the Form 10-K for information regarding spent nuclear fuel recovery, recovery of decommissioning costs, and the nuclear decommissioning trust fund. The fair value of the trust fund for Ameren Missouri’s Callaway Energy Center is reported as “Nuclear decommissioning trust fund” in Ameren’s and Ameren Missouri’s balance sheets. This amount is legally restricted and may be used only to fund the costs of nuclear decommissioning. Changes in the fair value of the trust fund are recorded as an increase or decrease to the nuclear decommissioning trust fund, with an offsetting adjustment to the related regulatory liability. Ameren and Ameren Missouri have recorded an ARO for the Callaway Energy Center decommissioning costs at fair value, which represents the present value of estimated future cash outflows. Annual decommissioning costs of $7 million are included in the costs used to establish electric rates for Ameren Missouri’s customers. Every three years, the MoPSC requires Ameren Missouri to file an updated cost study and funding analysis for decommissioning its Callaway Energy Center. An updated cost study and funding analysis was filed with the MoPSC in November 2020 and reflected within the ARO. In February 2021, the MoPSC approved no change in electric rates for decommissioning costs based on Ameren Missouri’s updated cost study funding analysis. See Note 13 – Supplemental Information for more information on Ameren Missouri’s AROs.

Maintenance Outage

See Note 9 – Callaway Energy Center under Part II, Item 8, of the Form 10-K for information regarding a maintenance outage from a non-nuclear operating issue related to the Callaway Energy Center’s generator in late December 2020 and subsequent return to service on August 4, 2021, along with the related insurance claims. In April 2022, Ameren Missouri received $22 million from NEIL related to lost sales insurance claims.

Insurance

The following table presents insurance coverage at Ameren Missouri’s Callaway Energy Center at September 30, 2022:


Type and Source of Coverage	Most Recent Renewal Date	Maximum Coverages			Maximum Assessments for Single Incidents
Public liability and nuclear worker liability:
American Nuclear Insurers	January 1, 2022	$	450		$	—
Pool participation	(a)	13,210		(a)	138		(b)
		$	13,660	(c)	$	138
Property damage:
NEIL and EMANI	April 1, 2022	$	3,200	(d)	$	26	(e)
Accidental outage:
NEIL	April 1, 2022	$	490	(f)	$	7	(e)

(a)Provided through mandatory participation in an industrywide retrospective premium assessment program. The maximum coverage available is dependent on the number of United States commercial reactors participating in the program.

(b)Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $450 million in the event of an incident at any licensed United States commercial reactor, payable at $21 million per year.

(c)Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. This limit is subject to change to account for the effects of inflation and changes in the number of licensed power reactors.

(d)NEIL provides $2.7 billion in property damage, stabilization, decontamination, and premature decommissioning insurance for radiation events and $2.3 billion in property damage insurance for nonradiation events. EMANI provides $490 million in property damage insurance for both radiation and nonradiation events.

(e)All NEIL-insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL.

(f)Accidental outage insurance provides for lost sales in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first 12 weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter for a total not exceeding the policy limit of $490 million. Nonradiation events are limited to $328 million.

The Price-Anderson Act is a federal law that limits the liability for claims from an incident involving any licensed United States commercial nuclear energy center. The limit is based on the number of licensed reactors. The limit of liability and the maximum potential annual payments are adjusted at least every five years for inflation to reflect changes in the Consumer Price Index. The most recent five-year inflationary adjustment became effective in November 2018. Owners of a nuclear reactor cover this exposure through a combination of private insurance and mandatory participation in a financial protection pool, as established by the Price-Anderson Act.

Losses resulting from terrorist attacks on nuclear facilities insured by NEIL are subject to industrywide aggregates, such that terrorist acts against one or more commercial nuclear power plants within a stated time period would be treated as a single event, and the owners of the nuclear power plants would share the limit of liability. NEIL policies have an aggregate limit of $3.2 billion within a 12-month period for radiation events, or $1.8 billion for events not involving radiation contamination, resulting from terrorist attacks. The EMANI policies are not subject to industrywide aggregates in the event of terrorist attacks on nuclear facilities.

If losses from a nuclear incident at the Callaway Energy Center exceed the limits of, or are not covered by insurance, or if coverage is unavailable, Ameren Missouri is at risk for any uninsured losses. If a serious nuclear incident were to occur, it could have a material adverse effect on Ameren’s and Ameren Missouri’s results of operations, financial position, or liquidity.

Retirement Benefits

9 Months Ended

Sep. 30, 2022

Retirement Benefits [Abstract]

RETIREMENT BENEFITS

The following table presents the components of the net periodic benefit cost (income) incurred for Ameren’s pension and postretirement benefit plans for the three and nine months ended September 30, 2022 and 2021:


	Pension Benefits								Postretirement Benefits
	Three Months				Nine Months				Three Months				Nine Months
	2022		2021		2022		2021		2022		2021		2022		2021
Service cost(a)	$	31	$	33	$	95	$	100	$	5	$	5	$	15	$	17
Non-service cost components:
Interest cost	42		38		123		114		8		9		25		25
Expected return on plan assets	(80)		(74)		(240)		(223)		(21)		(20)		(64)		(60)
Amortization of:

Prior service benefit	—		—		—		—		(1)		(1)		(3)		(3)
Actuarial loss (gain)	7		18		19		55		(5)		(1)		(14)		(4)
Total non-service cost components(b)	$	(31)	$	(18)	$	(98)	$	(54)	$	(19)	$	(13)	$	(56)	$	(42)

Net periodic benefit cost (income)(c)	$	—	$	15	$	(3)	$	46	$	(14)	$	(8)	$	(41)	$	(25)

(a)Service cost, net of capitalization, is reflected in “Operating Expenses – Other operations and maintenance” on Ameren’s statement of income.

(b)Non-service cost components are reflected in “Other Income, Net” on Ameren’s statement of income. See Note 5 – Other Income, Net, for additional information.

(c)Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.

Ameren Missouri and Ameren Illinois are responsible for their respective share of Ameren’s pension and other postretirement costs. The following table presents the respective share of net periodic pension and other postretirement benefit costs (income) incurred for the three and nine months ended September 30, 2022 and 2021:


	Pension Benefits								Postretirement Benefits
	Three Months				Nine Months				Three Months				Nine Months
	2022		2021		2022		2021		2022		2021		2022		2021
Ameren Missouri(a)	$	—	$	7	$	(2)	$	22	$	(3)	$	(1)	$	(10)	$	(3)
Ameren Illinois	1		8		2		25		(11)		(8)		(31)		(23)
Other	(1)		—		(3)		(1)		—		1		—		1
Ameren(a)	$	—	$	15	$	(3)	$	46	$	(14)	$	(8)	$	(41)	$	(25)

(a)Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.

- Definition

The entire disclosure for retirement benefits.

+ References

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+ Details

Income Taxes

9 Months Ended

Sep. 30, 2022

Income Tax Disclosure [Abstract]

Income Taxes

INCOME TAXES

The following table presents a reconciliation of the federal statutory corporate income tax rate to the effective income tax rate for the three and nine months ended September 30, 2022 and 2021:


	Ameren				Ameren Missouri				Ameren Illinois
	2022		2021		2022		2021		2022		2021
Three Months
Federal statutory corporate income tax rate	21	%	21	%	21	%	21	%	21	%	21	%
Increases (decreases) from:
Amortization of deferred investment tax credit	—		(1)		(1)		(1)		—		—
Amortization of excess deferred taxes(a)	(8)		(8)		(15)		(17)		(2)		(2)
Depreciation differences	—		—		—		—		—		(1)

Renewable and other tax credits(b)	(4)		(2)		(10)		(8)		—		—
State tax	4		4		3		4		7		7
Stock-based compensation	1		—		—		—		—		—
Cash surrender value of COLI	1		—		—		—		—		—
Effective income tax rate	15	%	14	%	(2)	%	(1)	%	26	%	25	%
Nine Months
Federal statutory corporate income tax rate	21	%	21	%	21	%	21	%	21	%	21	%
Increases (decreases) from:
Amortization of deferred investment tax credit	—		—		(1)		—		—		—
Amortization of excess deferred taxes(a)	(8)		(9)		(15)		(17)		(2)		(3)


Renewable and other tax credits(b)	(4)		(3)		(10)		(8)		—		—
State tax	5		5		3		3		7		7
Stock-based compensation	—		(1)		—		—		—		—
Effective income tax rate	14	%	13	%	(2)	%	(1)	%	26	%	25	%

(a)Reflects the amortization of amounts resulting from the revaluation of deferred income taxes subject to regulatory ratemaking, which are being refunded to customers. Deferred income taxes are revalued when federal or state income tax rates change, and the offset to the revaluation of deferred income taxes subject to regulatory ratemaking is recorded to a regulatory asset or liability.

(b)Includes credits associated with the High Prairie and Atchison renewable energy centers. Ameren Missouri placed the High Prairie Renewable Energy Center in service in December 2020. Additionally, Ameren Missouri placed in service the wind turbines at its Atchison Renewable Energy Center throughout the first half of 2021. The benefit of the credits associated with Missouri renewable energy standard compliance is refunded to customers through the RESRAM.

IRA

The IRA was enacted in August 2022, and includes various income tax provisions, among other things. The law extends federal production and investment tax credits for projects beginning construction through 2024 and allows for a 10% adder to the production and investment tax credits for siting projects at existing energy communities as defined in the law, which includes sites previously used for coal-fired generation. The law also creates clean energy tax credits for projects placed in service after 2024. The clean energy tax credits will apply to renewable energy production and investments, along with certain nuclear energy production, and will be phased out beginning in 2033, at the earliest. The phase-out is triggered when greenhouse gas emissions from the electric generation industry are reduced by at least 75% from the annual 2022 emission rate or at the beginning of 2033, whichever is later. The law allows for transferability to an unrelated party for cash of up to 100% of certain tax credits generated after 2022. In addition, the new law imposes a 15% minimum tax on adjusted financial statement income, as defined in the law, for corporations whose average annual adjusted financial statement income exceeds $1 billion for three consecutive preceding tax years effective for tax years beginning after December 31, 2022. Once a corporation exceeds this three-year average annual adjusted financial statement income threshold, it will be subject to the minimum tax for all future tax years. Ameren is currently evaluating the IRA and does not expect to be subject to the minimum tax imposed by the IRA in 2023. Implementation of the IRA provisions is subject to additional regulations, interpretations, amendments, or technical corrections that may be issued by the IRS or United States Department of Treasury.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Supplemental Information

9 Months Ended

Sep. 30, 2022

Supplemental Information [Abstract]

Supplemental Information

SUPPLEMENTAL INFORMATION

Cash, Cash Equivalents, and Restricted Cash

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets and the statements of cash flows at September 30, 2022, and December 31, 2021:


	September 30, 2022						December 31, 2021
	Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois
“Cash and cash equivalents”	$	7	$	—	$	—	$	8	$	—	$	—

Restricted cash included in “Other current assets”	7		3		4		16		4		6
Restricted cash included in “Other assets”	162		—		162		127		—		127
Restricted cash included in “Nuclear decommissioning trust fund”	4		4		—		4		4		—
Total cash, cash equivalents, and restricted cash	$	180	$	7	$	166	$	155	$	8	$	133

Restricted cash included in “Other current assets” primarily represents funds held by an irrevocable Voluntary Employee Beneficiary Association (VEBA) trust, which provides health care benefits for active employees. Restricted cash included in “Other assets” on Ameren’s and Ameren Illinois’ balance sheets primarily represents amounts collected under a cost recovery rider restricted for use in the procurement of renewable energy credits and amounts in a trust fund restricted for the use of funding certain asbestos-related claims.

Accounts Receivable

“Accounts receivable – trade” on Ameren’s and Ameren Illinois’ balance sheets include certain receivables purchased at a discount from alternative retail electric suppliers that elect to participate in the utility consolidated billing program. At September 30, 2022, and December 31, 2021, “Other current liabilities” on Ameren’s and Ameren Illinois’ balance sheets included payables for purchased receivables of $32 million and $27 million, respectively.

The following table provides a reconciliation of the beginning and ending amount of the allowance for doubtful accounts for the three and nine months ended September 30, 2022 and 2021:


	Three Months				Nine Months
	2022		2021		2022		2021
Ameren:
Beginning of period	$	30	$	42	$	29	$	50
Bad debt expense	15		7		26		8
Net write-offs	(14)		(13)		(24)		(22)
End of period	$	31	$	36	$	31	$	36
Ameren Missouri:
Beginning of period	$	12	$	16	$	13	$	16
Bad debt expense	3		2		6		5
Net write-offs	(3)		(4)		(7)		(7)
End of period	$	12	$	14	$	12	$	14
Ameren Illinois:(a)
Beginning of period	$	18	$	26	$	16	$	34
Bad debt expense	12		5		20		3		(b)
Net write-offs	(11)		(9)		(17)		(15)
End of period	$	19	$	22	$	19	$	22

(a)Ameren Illinois has rate-adjustment mechanisms that allow it to recover the difference between its actual net bad debt write-offs under GAAP, including those associated with receivables purchased from alternative retail electric suppliers, and the amount of net bad debt write-offs included in its base rates.

(b)In the nine months ended September 30, 2021, Ameren Illinois’ bad debt expense was reduced as a result of state funding received for customer bill assistance.

As of September 30, 2022, accounts receivable balances that were 30 days or greater past due or that were a part of a deferred payment arrangement represented 17%, 12%, and 21%, or $117 million, $39 million, and $78 million, of Ameren’s, Ameren Missouri’s, and Ameren Illinois’ customer trade receivables before allowance for doubtful accounts, respectively. In comparison, as of September 30, 2021, these percentages were 18%, 12%, and 25%, or $97 million, $33 million, and $64 million, for Ameren, Ameren Missouri, and Ameren Illinois, respectively.

Supplemental Cash Flow Information

Capital expenditures for the nine months ended September 30, 2021, at Ameren and Ameren Missouri included wind generation expenditures of $515 million.

The following table provides noncash financing and investing activity excluded from the statements of cash flows for the nine months ended September 30, 2022 and 2021:


	September 30, 2022						September 30, 2021
	Ameren		Ameren Missouri				Ameren Illinois	Ameren		Ameren Missouri		Ameren Illinois
Investing
Accrued capital expenditures	$	367	$	187	$	180		$	396	$	209	$	182

Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund	(262)		(262)		—			85		85		—
Financing
Issuance of common stock for stock-based compensation	$	31	$	—	$	—		$	33	$	—	$	—
Issuance of common stock under the DRPlus	8		—		—			—		—		—

Asset Retirement Obligations

The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the nine months ended September 30, 2022:


	Ameren Missouri			Ameren Illinois			Ameren
Balance at December 31, 2021	$	760	(a)	$	4	(b)	$	764	(a)
Liabilities incurred	1			—			1
Liabilities settled	(3)			—			(3)
Accretion	23		(c)	—			23		(c)
Change in estimates	(7)			—			(7)
Balance at September 30, 2022	$	774	(a)	$	4	(b)	$	778	(a)

(a)Balance included $7 million in “Other current liabilities” on the balance sheet as of both September 30, 2022, and December 31, 2021.

(b)Included in “Other deferred credits and liabilities” on the balance sheet.

(c)Accretion expense attributable to Ameren Missouri was recorded as a decrease to regulatory liabilities.

Stock-based Compensation

Ameren’s long-term incentive plan available for eligible employees, the 2014 Omnibus Incentive Compensation Plan (2014 Plan), was replaced prospectively for new grants only by the 2022 Omnibus Incentive Compensation Plan (2022 Plan) effective May 12, 2022. The 2022 Plan provides for a maximum of 8.8 million common shares to be available for grant to eligible employees and directors, and retains many of the features of the 2014 Plan. The 2022 Plan permits the grant of restricted stock, restricted stock units, stock options (incentive stock options and nonqualified stock options), stock appreciation rights, performance awards, cash-based awards and other stock-based awards.

In the first quarter of 2022 under the 2014 Plan, Ameren granted 267,849 performance share units with a grant date fair value of $25 million and 122,882 restricted share units with a grant date fair value of $11 million. Awards vest approximately 3 years after the grant date or on a pro-rata basis upon death or eligible retirement. The performance share units vest based on the achievement of certain specified market performance measures (229,566 performance share units) or clean energy transition targets (38,283 performance share units). The exact number of shares issued pursuant to a performance share unit varies from 0% to 200% of the target award, depending on actual company performance relative to the performance goals.

For the nine months ended September 30, 2022 and 2021, excess tax benefits associated with the settlement of stock-based compensation awards reduced income tax expense by $5 million in both periods.

Deferred Compensation

At September 30, 2022, and December 31, 2021, the present value of benefits to be paid for deferred compensation obligations was $88 million and $91 million, respectively, which was primarily reflected in “Other deferred credits and liabilities” on Ameren’s consolidated balance sheet.

Operating Revenues

As of September 30, 2022 and 2021, our remaining performance obligations for contracts with a term greater than one year were immaterial. The Ameren Companies elected not to disclose the aggregate amount of the transaction price allocated to the performance obligations that are unsatisfied as of the end of the reporting period for contracts with an initial expected term of one year or less.

See Note 14 – Segment Information for disaggregated revenue information.

Excise Taxes

Ameren Missouri and Ameren Illinois collect from their customers excise taxes, including municipal and state excise taxes and gross receipts taxes that are levied on the sale or distribution of natural gas and electricity. The following table presents the excise taxes recorded on a gross basis in “Operating Revenues – Electric,” “Operating Revenues – Natural gas” and “Operating Expenses – Taxes other than income taxes” on the statements of income for the three and nine months ended September 30, 2022 and 2021:


	Three Months				Nine Months
	2022		2021		2022		2021
Ameren Missouri	$	55	$	54	$	128	$	120
Ameren Illinois	28		27		101		93
Ameren	$	83	$	81	$	229	$	213

Earnings per Share

The following table reconciles the basic weighted-average number of common shares outstanding to the diluted weighted-average number of common shares outstanding for the three and nine months ended September 30, 2022 and 2021:


	Three Months		Nine Months
	2022	2021	2022	2021


Weighted-average Common Shares Outstanding – Basic	258.4	257.3	258.2	255.9
Assumed settlement of performance share units and restricted stock units	0.9	1.3	1.0	1.3
Dilutive effect of forward sale agreements	0.2	—	0.1	—
Weighted-average Common Shares Outstanding – Diluted(a)	259.5	258.6	259.3	257.2

(a)There was an immaterial number of anti-dilutive securities excluded from the earnings per diluted share calculations for the three and nine months ended September 30, 2022 and 2021.

Segment Information

9 Months Ended

Sep. 30, 2022

Segment Reporting [Abstract]

SEGMENT INFORMATION

The following tables present revenues, net income attributable to common shareholders, and capital expenditures by segment at Ameren and Ameren Illinois for the three and nine months ended September 30, 2022 and 2021. Ameren, Ameren Missouri, and Ameren Illinois management review segment capital expenditure information rather than any individual or total asset amount. For additional information about our segments, see Note 16 – Segment Information under Part II, Item 8, of the Form 10-K.

Ameren


	Ameren Missouri			Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission			Other		Intersegment Eliminations		Ameren
Three Months 2022:
External revenues	$	1,351		$	672	$	146	$	137		$	—	$	—	$	2,306
Intersegment revenues	8			—		—		32			—		(40)		—
Net income (loss) attributable to Ameren common shareholders	397			51		(4)		78		(a)	(70)		—		452
Capital expenditures	431			163		114		187			1		3		899
Three Months 2021:
External revenues	$	1,118		$	425	$	127	$	141		$	—	$	—	$	1,811
Intersegment revenues	11			3		—		19			—		(33)		—
Net income (loss) attributable to Ameren common shareholders	375			36		(8)		73		(a)	(51)		—		425
Capital expenditures	466		(b)	143		93		154			2		(8)		850		(b)
Nine Months 2022:
External revenues	$	3,071		$	1,640	$	811	$	389		$	—	$	—	$	5,911
Intersegment revenues	25			1		—		76			—		(102)		—
Net income (loss) attributable to Ameren common shareholders	547			151		82		199		(a)	(68)		—		911
Capital expenditures	1,237			444		232		519			4		1		2,437
Nine Months 2021:
External revenues	$	2,612		$	1,222	$	642	$	373		$	—	$	—	$	4,849
Intersegment revenues	30			5		—		53			—		(88)		—
Net income (loss) attributable to Ameren common shareholders	533			123		75		175		(a)	(41)		—		865
Capital expenditures	1,567		(b)	429		202		426			3		(14)		2,613		(b)

(a)Ameren Transmission earnings reflect an allocation of financing costs from Ameren (parent).

(b)Includes $98 million and $515 million at Ameren and Ameren Missouri for wind generation expenditures for the three and nine months ended September 30, 2021, respectively.

Ameren Illinois


	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Intersegment Eliminations		Ameren Illinois
Three Months 2022:
External revenues	$	672	$	146	$	86	$	—	$	904
Intersegment revenues	—		—		31		(31)		—
Net income (loss) available to common shareholder	51		(4)		56		—		103
Capital expenditures	163		114		169		—		446
Three Months 2021:
External revenues	$	428	$	127	$	90	$	—	$	645
Intersegment revenues	—		—		18		(18)		—
Net income (loss) available to common shareholder	36		(8)		51		—		79
Capital expenditures	143		93		144		—		380


	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Intersegment Eliminations		Ameren Illinois
Nine Months 2022:
External revenues	$	1,641	$	811	$	245	$	—	$	2,697
Intersegment revenues	—		—		75		(75)		—
Net income available to common shareholder	151		82		142		—		375
Capital expenditures	444		232		469		—		1,145
Nine Months 2021:
External revenues	$	1,227	$	642	$	228	$	—	$	2,097
Intersegment revenues	—		—		49		(49)		—
Net income available to common shareholder	123		75		116		—		314
Capital expenditures	429		202		395		—		1,026

The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the three and nine months ended September 30, 2022 and 2021. Economic factors affect the nature, timing, amount, and uncertainty of revenues and cash flows in a similar manner across customer classes. Revenues from alternative revenue programs have a similar distribution among customer classes as revenues from contracts with customers. Other revenues not associated with contracts with customers are presented in the Other customer classification, along with electric transmission and off-system revenues.

Ameren


	Ameren Missouri		Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission		Intersegment Eliminations		Ameren
Three Months 2022:
Residential	$	564	$	407	$	—	$	—	$	—	$	971
Commercial	430		233		—		—		—		663
Industrial	99		47		—		—		—		146
Other	245		(15)		—		169		(39)		360
Total electric revenues	$	1,338	$	672	$	—	$	169	$	(39)	$	2,140
Residential	$	11	$	—	$	89	$	—	$	—	$	100
Commercial	6		—		25		—		—		31
Industrial	1		—		5		—		—		6
Other	3		—		27		—		(1)		29
Total natural gas revenues	$	21	$	—	$	146	$	—	$	(1)	$	166
Total revenues(a)	$	1,359	$	672	$	146	$	169	$	(40)	$	2,306
Three Months 2021:
Residential	$	537	$	258	$	—	$	—	$	—	$	795
Commercial	412		143		—		—		—		555
Industrial	98		26		—		—		—		124
Other	66		1		—		160		(33)		194
Total electric revenues	$	1,113	$	428	$	—	$	160	$	(33)	$	1,668
Residential	$	9	$	—	$	75	$	—	$	—	$	84
Commercial	4		—		23		—		—		27
Industrial	—		—		3		—		—		3
Other	3		—		26		—		—		29
Total natural gas revenues	$	16	$	—	$	127	$	—	$	—	$	143
Total revenues(a)	$	1,129	$	428	$	127	$	160	$	(33)	$	1,811


	Ameren Missouri		Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission		Intersegment Eliminations		Ameren
Nine Months 2022:
Residential	$	1,267	$	954	$	—	$	—	$	—	$	2,221
Commercial	968		571		—		—		—		1,539
Industrial	229		145		—		—		—		374
Other	502		(29)		—		465		(101)		837
Total electric revenues	$	2,966	$	1,641	$	—	$	465	$	(101)	$	4,971
Residential	$	78	$	—	$	575	$	—	$	—	$	653
Commercial	36		—		152		—		—		188
Industrial	4		—		33		—		—		37
Other	12		—		51		—		(1)		62
Total natural gas revenues	$	130	$	—	$	811	$	—	$	(1)	$	940
Total revenues(a)	$	3,096	$	1,641	$	811	$	465	$	(102)	$	5,911
Nine Months 2021:
Residential	$	1,177	$	705	$	—	$	—	$	—	$	1,882
Commercial	899		402		—		—		—		1,301
Industrial	221		94		—		—		—		315
Other	246		26		—		426		(88)		610
Total electric revenues	$	2,543	$	1,227	$	—	$	426	$	(88)	$	4,108
Residential	$	54	$	—	$	438	$	—	$	—	$	492
Commercial	23		—		116		—		—		139
Industrial	2		—		20		—		—		22
Other	20		—		68		—		—		88
Total natural gas revenues	$	99	$	—	$	642	$	—	$	—	$	741
Total revenues(a)	$	2,642	$	1,227	$	642	$	426	$	(88)	$	4,849

(a)The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the three and nine months ended September 30, 2022 and 2021:


	Ameren Missouri			Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission		Ameren
Three Months 2022:
Revenues from alternative revenue programs	$	14		$	(83)	$	(3)	$	(11)	$	(83)
Other revenues not from contracts with customers	(45)		(a)	2		—		—		(43)		(a)
Three Months 2021:
Revenues from alternative revenue programs	$	6		$	(97)	$	(5)	$	1	$	(95)
Other revenues not from contracts with customers	7		(b)	6		—		—		13		(b)
Nine Months 2022:
Revenues from alternative revenue programs	$	8		$	13	$	(5)	$	(14)	$	2
Other revenues not from contracts with customers	(81)		(a), (b)	5		2		—		(74)		(a), (b)
Nine Months 2021:
Revenues from alternative revenue programs	$	(9)		$	(2)	$	—	$	5	$	(6)
Other revenues not from contracts with customers	71		(b)	9		2		—		82		(b)

(a)Includes net realized losses on derivative power contracts.

(b)Includes insurance recoveries related to lost sales associated with the Callaway Energy Center maintenance outage. See Note 9 – Callaway Energy Center under Part II, Item 8, of the Form 10-K for additional information.

Ameren Illinois


	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Intersegment Eliminations		Ameren Illinois
Three Months 2022:
Residential	$	407	$	89	$	—	$	—	$	496
Commercial	233		25		—		—		258
Industrial	47		5		—		—		52
Other	(15)		27		117		(31)		98
Total revenues(a)	$	672	$	146	$	117	$	(31)	$	904
Three Months 2021:
Residential	$	258	$	75	$	—	$	—	$	333
Commercial	143		23		—		—		166
Industrial	26		3		—		—		29
Other	1		26		108		(18)		117
Total revenues(a)	$	428	$	127	$	108	$	(18)	$	645
Nine Months 2022:
Residential	$	954	$	575	$	—	$	—	$	1,529
Commercial	571		152		—		—		723
Industrial	145		33		—		—		178
Other	(29)		51		320		(75)		267
Total revenues(a)	$	1,641	$	811	$	320	$	(75)	$	2,697
Nine Months 2021:
Residential	$	705	$	438	$	—	$	—	$	1,143
Commercial	402		116		—		—		518
Industrial	94		20		—		—		114
Other	26		68		277		(49)		322
Total revenues(a)	$	1,227	$	642	$	277	$	(49)	$	2,097

(a)The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the Ameren Illinois segments for the three and nine months ended September 30, 2022 and 2021:


	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Ameren Illinois
Three Months 2022:
Revenues from alternative revenue programs	$	(83)	$	(3)	$	(10)	$	(96)
Other revenues not from contracts with customers	2		—		—		2

Three Months 2021:
Revenues from alternative revenue programs	$	(97)	$	(5)	$	3	$	(99)
Other revenues not from contracts with customers	6		—		—		6

Nine Months 2022:
Revenues from alternative revenue programs	$	13	$	(5)	$	(12)	$	(4)
Other revenues not from contracts with customers	5		2		—		7

Nine Months 2021:
Revenues from alternative revenue programs	$	(2)	$	—	$	4	$	2
Other revenues not from contracts with customers	9		2		—		11

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Summary Of Significant Accounting Policies (Policies)	9 Months Ended
Summary Of Significant Accounting Policies (Policies)	Sep. 30, 2022
Accounting Policies [Abstract]
Nature of Operations	Ameren, headquartered in St. Louis, Missouri, is a public utility holding company whose primary assets are its equity interests in its subsidiaries. Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. Dividends on Ameren’s common stock and the payment of expenses by Ameren depend on distributions made to it by its subsidiaries. Ameren’s principal subsidiaries are listed below. Ameren has other subsidiaries that conduct other activities, such as providing shared services. •Union Electric Company, doing business as Ameren Missouri, operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri. •Ameren Illinois Company, doing business as Ameren Illinois, operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois. •ATXI operates a FERC rate-regulated electric transmission business in the MISO.
Consolidation	Ameren’s and Ameren Missouri’s financial statements are prepared on a consolidated basis and therefore include the accounts of their majority-owned subsidiaries. All intercompany transactions have been eliminated. Ameren Missouri’s subsidiaries were created for the ownership of renewable generation projects. Ameren Illinois has no subsidiaries. All tabular dollar amounts are in millions, unless otherwise indicated. Our accounting policies conform to GAAP. Our financial statements reflect all adjustments (which include normal, recurring adjustments) that are necessary, in our opinion, for a fair presentation of our results. The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions. Such estimates and assumptions affect reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of financial statements, and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. The results of operations for an interim period may not give a true indication of results that may be expected for a full year. These financial statements should be read in conjunction with the financial statements and accompanying notes included in the Form 10-K.
Consolidation, Variable Interest Entity, Policy	Variable Interest Entities As of September 30, 2022, and December 31, 2021, Ameren had unconsolidated variable interests as a limited partner in various equity method investments, primarily to advance clean and resilient energy technologies, totaling $58 million and $56 million, respectively, included in “Other assets” on Ameren’s consolidated balance sheet. Any earnings or losses related to these investments are included in “Other Income, Net” on Ameren’s consolidated statement of income and comprehensive income. Ameren is not the primary beneficiary of these investments because it does not have the power to direct matters that most significantly affect the activities of these variable interest entities. As of September 30, 2022, the maximum exposure to loss related to these variable interests is limited to the investment in these partnerships of $58 million plus associated outstanding funding commitments of $21 million.
Life Insurance, Corporate Or Bank Owned	COLIAmeren and Ameren Illinois have COLI, which is recorded at the net cash surrender value. The net cash surrender value is the amount that can be realized under the insurance policies at the balance sheet date.
Derivatives, Policy	We use derivatives to manage the risk of changes in market prices for natural gas, power, and uranium, as well as the risk of changes in rail transportation surcharges through fuel oil hedges. Such price fluctuations may cause the following: •an unrealized appreciation or depreciation of our contracted commitments to purchase or sell when purchase or sale prices under the commitments are compared with current commodity prices; •market values of natural gas and uranium inventories that differ from the cost of those commodities in inventory; •actual cash outlays for the purchase of these commodities that differ from anticipated cash outlays; and •actual off-system sales revenues that differ from anticipated revenues. The derivatives that we use to hedge these risks are governed by our risk management policies for forward contracts, futures, options, and swaps. Our net positions are continually assessed within our structured hedging programs to determine whether new or offsetting transactions are required. The goal of the hedging program is generally to mitigate financial risks while ensuring that sufficient volumes are available to meet our requirements. Contracts we enter into as part of our risk management program may be settled financially, settled by physical delivery, or net settled with the counterparty. All contracts considered to be derivative instruments are required to be recorded on the balance sheet at their fair values, unless the NPNS exception applies. Many of our physical contracts, such as our purchased power contracts, qualify for the NPNS exception to derivative accounting rules. The revenue or expense on NPNS contracts is recognized at the contract price upon physical delivery. The following disclosures exclude NPNS contracts and other non-derivative commodity contracts that are accounted for under the accrual method of accounting. If we determine that a contract meets the definition of a derivative and is not eligible for the NPNS exception, we review the contract to determine whether the resulting gains or losses qualify for regulatory deferral. Derivative contracts that qualify for regulatory deferral are recorded at fair value, with changes in fair value recorded as regulatory assets or liabilities in the period in which the change occurs. We believe derivative losses and gains deferred as regulatory assets and liabilities are probable of recovery, or refund, through future rates charged to customers. Regulatory assets and liabilities are amortized to operating income as related losses and gains are reflected in rates charged to customers. Therefore, gains and losses on these derivatives have no effect on operating income.We believe that entering into master netting arrangements or similar agreements mitigates the level of financial loss that could result from default by allowing net settlement of derivative assets and liabilities. These master netting arrangements allow the counterparties to net settle sale and purchase transactions. Further, collateral requirements are calculated at the master netting arrangement or similar agreement level by counterparty.
Deferred Compensation	Deferred Compensation At September 30, 2022, and December 31, 2021, the present value of benefits to be paid for deferred compensation obligations was $88 million and $91 million, respectively, which was primarily reflected in “Other deferred credits and liabilities” on Ameren’s consolidated balance sheet.
Revenue from Contract with Customer	Operating Revenues As of September 30, 2022 and 2021, our remaining performance obligations for contracts with a term greater than one year were immaterial. The Ameren Companies elected not to disclose the aggregate amount of the transaction price allocated to the performance obligations that are unsatisfied as of the end of the reporting period for contracts with an initial expected term of one year or less. See Note 14 – Segment Information for disaggregated revenue information.
Excise Taxes	Excise TaxesAmeren Missouri and Ameren Illinois collect from their customers excise taxes, including municipal and state excise taxes and gross receipts taxes that are levied on the sale or distribution of natural gas and electricity.

- Definition

Disclosure of accounting policy for revenue from contract with customer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

Short-Term Debt and Liquidity (Tables)

9 Months Ended

Sep. 30, 2022

Debt Disclosure [Abstract]

Schedule of Short-term Debt

The following table presents commercial paper outstanding, net of issuance discounts, as of September 30, 2022, and December 31, 2021. There were no borrowings outstanding under the Credit Agreements as of September 30, 2022, or December 31, 2021.


	September 30, 2022		December 31, 2021
Ameren (parent)	$	690	$	277
Ameren Missouri	178		165
Ameren Illinois	353		103
Ameren consolidated	$	1,221	$	545

The following table summarizes the activity and relevant interest rates for Ameren (parent)’s, Ameren Missouri’s, and Ameren Illinois’ commercial paper issuances and borrowings under the Credit Agreements in the aggregate for the nine months ended September 30, 2022 and 2021:


	Ameren (parent)			Ameren Missouri			Ameren Illinois			Ameren Consolidated
2022
Average daily amount outstanding	$	439		$	253		$	99		$	791

Weighted-average interest rate	1.58		%	1.16		%	1.77		%	1.47		%
Peak amount outstanding during period(a)	$	690		$	539		$	354		$	1,222
Peak interest rate	3.55		%	3.55		%	3.60		%	3.60		%
2021
Average daily amount outstanding	$	404		$	121		$	140		$	665

Weighted-average interest rate	0.23		%	0.22		%	0.22		%	0.22		%
Peak amount outstanding during period(a)	$	650		$	546		$	485		$	1,134
Peak interest rate	0.33		%	0.25		%	0.25		%	0.33		%

(a)The timing of peak outstanding commercial paper issuances and borrowings under the Credit Agreements varies by company. Therefore, the sum of individual company peak amounts may not equal the Ameren consolidated peak for the period.

Other Income, Net (Tables)

9 Months Ended

Sep. 30, 2022

Other Nonoperating Income (Expense) [Abstract]

Other Income And Expenses

The following table presents the components of “Other Income, Net” in the Ameren Companies’ statements of income for the three and nine months ended September 30, 2022 and 2021:


	Three Months				Nine Months
	2022		2021		2022		2021
Ameren:

Allowance for equity funds used during construction	$	12	$	14	$	31	$	30
Interest income on industrial development revenue bonds	6		7		18		19


Non-service cost components of net periodic benefit income(a)	45		34		138		102
Miscellaneous income	5		1		14		7
Earnings (losses) related to equity method investments	(3)		2		1		8
Donations	(1)		(1)		(5)		(5)
Miscellaneous expense	(6)		(1)		(17)		(10)
Total Other Income, Net	$	58	$	56	$	180	$	151
Ameren Missouri:

Allowance for equity funds used during construction	$	7	$	7	$	17	$	17
Interest income on industrial development revenue bonds	6		7		18		19

Non-service cost components of net periodic benefit income(a)	13		13		41		41
Miscellaneous income	2		2		5		3
Donations	—		—		(2)		(1)
Miscellaneous expense	(3)		(2)		(7)		(5)
Total Other Income, Net	$	25	$	27	$	72	$	74
Ameren Illinois:

Allowance for equity funds used during construction	$	5	$	7	$	14	$	13


Non-service cost components of net periodic benefit income	21		13		63		41
Miscellaneous income	4		—		9		4
Donations	(1)		(1)		(3)		(4)
Miscellaneous expense	(3)		—		(8)		(5)
Total Other Income, Net	$	26	$	19	$	75	$	49

(a)For the three and nine months ended September 30, 2022, the non-service cost components of net periodic benefit income were adjusted by amounts deferred of $5 million and $16 million, respectively, due to a regulatory tracking mechanism for the difference between the level of such costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates. The deferral was $(3) million and $(6) million for both the three and nine months ended September 30, 2021, respectively. See Note 11– Retirement Benefits for additional information.

Derivative Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2022

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Open Gross Derivative Volumes By Commodity Type

The following table presents open gross commodity contract volumes by commodity type for derivative assets and liabilities as of September 30, 2022, and December 31, 2021. As of September 30, 2022, these contracts extended through October 2024, October 2027, May 2032 and March 2024 for fuel oils, natural gas, power and uranium, respectively:


	Quantity (in millions)
	September 30, 2022			December 31, 2021
Commodity	Ameren Missouri	Ameren Illinois	Ameren	Ameren Missouri	Ameren Illinois	Ameren
Fuel oils (in gallons)	19	—	19	30	—	30
Natural gas (in mmbtu)	43	144	187	35	144	179
Power (in MWhs)	2	6	8	6	6	12
Uranium (pounds in thousands)	406	—	406	586	—	586

Derivative Instruments Carrying Value

The following table presents the carrying value and balance sheet location of all derivative commodity contracts, none of which were designated as hedging instruments, as of September 30, 2022, and December 31, 2021:


			September 30, 2022					December 31, 2021
	Balance Sheet Location		Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren







Fuel oils	Other current assets		12		—		12			8		—		8
	Other assets		3		—		3			5		—		5
Natural gas	Mark-to-market derivative assets		(a)		57		(a)			(a)		28		(a)

	Other current assets		14		—		71			7		—		35
	Other assets		13		21		34			5		13		18
Power	Mark-to-market derivative assets		(a)		11		(a)			(a)		—		(a)

	Other current assets		28		—		39			23		—		23
	Other assets		—		5		5			—		—		—


Uranium	Other current assets		2		—		2			—		—		—
	Other assets		1		—		1			1		—		1
	Total assets	$	73	$	94	$	167		$	49	$	41	$	90



Fuel oils	Other deferred credits and liabilities		1		—		1			—		—		—
Natural gas	Mark-to-market derivative liabilities		2		(a)		(a)			2		(a)		(a)

	Other current liabilities		—		9		11			—		6		8
	Other deferred credits and liabilities		1		3		4			1		2		3
Power	Mark-to-market derivative liabilities		111		(a)		(a)			50		(a)		(a)

	Other current liabilities		—		—		111			—		9		59
	Other deferred credits and liabilities		14		36		50			23		108		131
Uranium	Mark-to-market derivative liabilities		—		(a)		(a)			1		(a)		(a)

	Other current liabilities		—		—		—			—		—		1

	Total liabilities	$	129	$	48	$	177		$	77	$	125	$	202

(a)Balance sheet line item not applicable to registrant.

Offsetting Assets and Liabilities

The following table provides the recognized gross derivative balances and the net amounts of those derivatives subject to an enforceable master netting arrangement or similar agreement as of September 30, 2022, and December 31, 2021:


			Gross Amounts Not Offset in the Balance Sheet
Commodity Contracts Eligible to be Offset	Gross Amounts Recognized in the Balance Sheet		Derivative Instruments		Cash Collateral Received/Posted(a)		Net Amount
September 30, 2022
Assets:
Ameren Missouri	$	73	$	18	$	2	$	53
Ameren Illinois	94		13		1		80
Ameren	$	167	$	31	$	3	$	133
Liabilities:
Ameren Missouri	$	129	$	18	$	99	$	12
Ameren Illinois	48		13		—		35
Ameren	$	177	$	31	$	99	$	47
December 31, 2021
Assets:
Ameren Missouri	$	49	$	15	$	—	$	34
Ameren Illinois	41		4		—		37
Ameren	$	90	$	19	$	—	$	71
Liabilities:
Ameren Missouri	$	77	$	15	$	47	$	15
Ameren Illinois	125		4		—		121
Ameren	$	202	$	19	$	47	$	136

(a)Cash collateral received reduces gross asset balances and is included in “Other current liabilities” and “Other deferred credits and liabilities” on the balance sheet. Cash collateral posted reduces gross liability balances and is included in “Current collateral assets” and “Other assets” on the balance sheet for Ameren and Ameren Missouri and “Other current assets” and “Other assets” for Ameren Illinois.

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2022

Fair Value Disclosures [Abstract]

Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis

The following table sets forth, by level within the fair value hierarchy, our assets and liabilities measured at fair value on a recurring basis as of September 30, 2022, and December 31, 2021:


		September 30, 2022									December 31, 2021
		Level 1		Level 2		Level 3		Total			Level 1		Level 2		Level 3		Total
Assets:
Ameren Missouri
	Derivative assets – commodity contracts:
	Fuel oils	$	13	$	—	$	2	$	15		$	13	$	—	$	—	$	13
	Natural gas	1		26		—		27			—		12		—		12
	Power	9		—		19		28			10		—		13		23
	Uranium	—		—		3		3			—		—		1		1
	Total derivative assets – commodity contracts	$	23	$	26	$	24	$	73		$	23	$	12	$	14	$	49
	Nuclear decommissioning trust fund:

	Equity securities:
	U.S. large capitalization	$	574	$	—	$	—	$	574		$	824	$	—	$	—	$	824
	Debt securities:
	U.S. Treasury and agency securities	—		148		—		148			—		141		—		141
	Corporate bonds	—		115		—		115			—		131		—		131


	Other	—		64		—		64			—		56		—		56
	Total nuclear decommissioning trust fund	$	574	$	327	$	—	$	901	(a)	$	824	$	328	$	—	$	1,152	(a)
	Total Ameren Missouri	$	597	$	353	$	24	$	974		$	847	$	340	$	14	$	1,201
Ameren Illinois
	Derivative assets – commodity contracts:
	Natural gas	$	6	$	65	$	7	$	78		$	1	$	33	$	7	$	41
	Power	—		—		16		16			—		—		—		—
	Total Ameren Illinois	$	6	$	65	$	23	$	94		$	1	$	33	$	7	$	41
Ameren
	Derivative assets – commodity contracts(b)	$	29	$	91	$	47	$	167		$	24	$	45	$	21	$	90
	Nuclear decommissioning trust fund(c)	574		327		—		901		(a)	824		328		—		1,152		(a)
	Total Ameren	$	603	$	418	$	47	$	1,068		$	848	$	373	$	21	$	1,242
Liabilities:
Ameren Missouri
	Derivative liabilities – commodity contracts:
	Fuel oils	$	1	$	—	$	—	$	1		$	—	$	—	$	—	$	—
	Natural gas	—		2		1		3			—		2		1		3
	Power	98		—		27		125			45		—		28		73
	Uranium	—		—		—		—			—		—		1		1
	Total Ameren Missouri	$	99	$	2	$	28	$	129		$	45	$	2	$	30	$	77
Ameren Illinois
	Derivative liabilities – commodity contracts:
	Natural gas	$	—	$	6	$	6	$	12		$	—	$	5	$	3	$	8
	Power	—		—		36		36			—		—		117		117
	Total Ameren Illinois	$	—	$	6	$	42	$	48		$	—	$	5	$	120	$	125
Ameren
	Derivative liabilities – commodity contracts(b)	$	99	$	8	$	70	$	177		$	45	$	7	$	150	$	202

(a)Balance excludes $9 million and $7 million of cash and cash equivalents, receivables, payables, and accrued income, net, for September 30, 2022, and December 31, 2021, respectively.

(b)See the Ameren Missouri and Ameren Illinois sections of the table for a breakout of the fair value of Ameren’s derivative assets and liabilities by type of commodity.

(c)See the Ameren Missouri section of the table for a breakout of the fair value of Ameren’s nuclear decommissioning trust fund by investment type.

Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy

The following table presents the fair value reconciliation of Level 3 power derivative contract assets and liabilities measured at fair value on a recurring basis for the three and nine months ended September 30, 2022 and 2021:


	2022						2021
	Ameren Missouri		Ameren Illinois		Ameren			Ameren Missouri		Ameren Illinois		Ameren
For the three months ended September 30:
Beginning balance at July 1	$	(36)	$	(44)	$	(80)		$	(5)	$	(166)	$	(171)
Realized and unrealized gains/(losses) included in regulatory assets/liabilities	(10)		30		20			(16)		19		3


Settlements	38		(6)		32			(2)		3		1


Ending balance at September 30	$	(8)	$	(20)	$	(28)		$	(23)	$	(144)	$	(167)
Change in unrealized gains/(losses) related to assets/liabilities held at September 30	$	(3)	$	28	$	25		$	(17)	$	19	$	2
For the nine months ended September 30:
Beginning balance at January 1	$	(15)	$	(117)	$	(132)		$	2	$	(198)	$	(196)
Realized and unrealized gains/(losses) included in regulatory assets/liabilities	(56)		105		49			(22)		43		21


Settlements	63		(8)		55			(3)		11		8


Ending balance at September 30	$	(8)	$	(20)	$	(28)		$	(23)	$	(144)	$	(167)
Change in unrealized gains/(losses) related to assets/liabilities held at September 30	$	(39)	$	100	$	61		$	(21)	$	42	$	21

Fair Value, Assets and Liabilities Measured on Nonrecurring Basis, Valuation Techniques

The following table describes the valuation techniques and significant unobservable inputs utilized for the fair value of our Level 3 power derivative contract assets and liabilities as of September 30, 2022, and December 31, 2021:


			Fair Value						Weighted Average(b)
	Commodity		Assets		Liabilities	Valuation Technique(s)	Unobservable Input(a)	Range









2022	Power(c)	$	35	$	(63)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps ($/MWh)	42 – 118	60

							Nodal basis ($/MWh)	(15) – 2	(5)


							Trend rate (%)	0 – 1	0








































2021	Power(d)	$	13	$	(145)	Discounted cash flow	Average forward peak and off-peak pricing – forwards/swaps ($/MWh)	32 – 55	40

							Nodal basis ($/MWh)	(14) – 0	(2)


							Trend rate (%)	(e)	0

(a)Generally, significant increases (decreases) in these inputs in isolation would result in a significantly higher (lower) fair value measurement.

(b)Unobservable inputs were weighted by relative fair value.

(c)Valuations through 2031 use visible forward prices adjusted for nodal-to-hub basis differentials. Valuations beyond 2031 use a trend rate factor and are similarly adjusted for nodal-to-hub basis differentials.

(d)Valuations through 2029 use visible forward prices adjusted for nodal-to-hub basis differentials. Valuations beyond 2029 use a trend rate factor and are similarly adjusted for nodal-to-hub basis differentials.

(e)No meaningful range around weighted average.

Schedule of Financial Assets and Liabilities

The following table sets forth the carrying amount and, by level within the fair value hierarchy, the fair value of financial assets and liabilities disclosed, but not recorded, at fair value as of September 30, 2022, and December 31, 2021:


	Carrying Amount			Fair Value
				Level 1		Level 2		Level 3			Total
	September 30, 2022
Ameren:
Cash, cash equivalents, and restricted cash	$	180		$	180	$	—	$	—		$	180
Investments in industrial development revenue bonds(a)	248			—		248		—			248
Short-term debt	1,221			—		1,221		—			1,221
Long-term debt (including current portion)(a)	13,732		(b)	—		11,493		446		(c)	11,939
Ameren Missouri:
Cash, cash equivalents, and restricted cash	$	7		$	7	$	—	$	—		$	7

Investments in industrial development revenue bonds(a)	248			—		248		—			248
Short-term debt	178			—		178		—			178

Long-term debt (including current portion)(a)	6,140		(b)	—		5,352		—			5,352
Ameren Illinois:
Cash, cash equivalents, and restricted cash	$	166		$	166	$	—	$	—		$	166

Short-term debt	353			—		353		—			353

Long-term debt (including current portion)	4,489		(b)	—		3,868		—			3,868
	December 31, 2021
Ameren:
Cash, cash equivalents, and restricted cash	$	155		$	155	$	—	$	—		$	155
Investments in industrial development revenue bonds(a)	248			—		248		—			248
Short-term debt	545			—		545		—			545
Long-term debt (including current portion)(a)	13,067		(b)	—		13,930		591		(c)	14,521
Ameren Missouri:
Cash, cash equivalents, and restricted cash	$	8		$	8	$	—	$	—		$	8

Investments in industrial development revenue bonds(a)	248			—		248		—			248
Short-term debt	165			—		165		—			165
Long-term debt (including current portion)(a)	5,619		(b)	—		6,321		—			6,321
Ameren Illinois:
Cash, cash equivalents, and restricted cash	$	133		$	133	$	—	$	—		$	133
Short-term debt	103			—		103		—			103

Long-term debt (including current portion)	4,392		(b)	—		4,971		—			4,971

(a)Ameren and Ameren Missouri have investments in industrial development revenue bonds, classified as held-to-maturity and recorded in “Other Assets,” that are equal to the finance obligations for the Peno Creek and Audrain CT energy centers. As of September 30, 2022, and December 31, 2021, the carrying amount of both the investments in industrial development revenue bonds and the finance obligations approximated fair value.

(b)Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $99 million, $42 million, and $41 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of September 30, 2022. Included unamortized debt issuance costs, which were excluded from the fair value measurement, of $94 million, $38 million, and $39 million for Ameren, Ameren Missouri, and Ameren Illinois, respectively, as of December 31, 2021.

(c)The Level 3 fair value amount consists of ATXI’s senior unsecured notes.

Related Party Transactions (Tables)

9 Months Ended

Sep. 30, 2022

Schedule of Affiliate Receivables and Payables

The following table presents the affiliate balances related to income taxes for Ameren Missouri and Ameren Illinois as of September 30, 2022, and December 31, 2021:


	September 30, 2022				December 31, 2021
	Ameren Missouri		Ameren Illinois		Ameren Missouri		Ameren Illinois
Income taxes payable to parent(a)	$	—	$	72	$	—	$	8
Income taxes receivable from parent(b)	12		—		27		18

(a)Included in “Accounts payable – affiliates” on the balance sheet.

(b)Included in “Accounts receivable – affiliates” on the balance sheet.

Schedule of Related Party Transactions

The following table presents the impact on Ameren Missouri and Ameren Illinois of related-party transactions for the three and nine months ended September 30, 2022 and 2021:


				Three Months				Nine Months
Agreement	Income Statement Line Item			Ameren Missouri		Ameren Illinois		Ameren Missouri		Ameren Illinois
Ameren Missouri power supply	Operating Revenues	2022	$	2	$	(a)	$	7	$	(a)
agreements with Ameren Illinois		2021		5		(a)		10		(a)
Ameren Missouri and Ameren Illinois	Operating Revenues	2022	$	6	$	(b)	$	18	$	(b)
rent and facility services		2021		6		(b)		20		(b)
Ameren Missouri and Ameren Illinois miscellaneous	Operating Revenues	2022	$	(b)	$	(b)	$	(b)	$	1
services		2021		(b)		3		(b)		5
Total Operating Revenues		2022	$	8	$	(b)	$	25	$	1
		2021		11		3		30		5
Ameren Illinois power supply	Purchased Power	2022	$	(a)	$	2	$	(a)	$	7
agreements with Ameren Missouri		2021		(a)		5		(a)		10
Ameren Missouri and Ameren Illinois	Purchased Power	2022	$	1	$	(b)	$	1	$	(b)
transmission services from ATXI		2021		1		(b)		3		1
Total Purchased Power		2022	$	1	$	2	$	1	$	7
		2021		1		5		3		11
Ameren Missouri and Ameren Illinois	Other Operations and Maintenance	2022	$	(b)	$	1	$	(b)	$	2
rent and facility services		2021		(b)		1		(b)		3
Ameren Services support services	Other Operations and Maintenance	2022	$	38	$	36	$	109	$	103
agreement		2021		41		37		110		101
Total Other Operations and		2022	$	38	$	37	$	109	$	105
Maintenance		2021		41		38		110		104
Money pool borrowings (advances)	(Interest Charges)/Other Income, Net	2022	$	(b)	$	(b)	$	(b)	$	(b)
		2021		(b)		(b)		(b)		(b)

(a)Not applicable.

(b)Amount less than $1 million.

Callaway Energy Center (Tables)

9 Months Ended

Sep. 30, 2022

Nuclear Waste Matters [Abstract]

Schedule of Insurance Coverage at Callaway Energy Center

The following table presents insurance coverage at Ameren Missouri’s Callaway Energy Center at September 30, 2022:


Type and Source of Coverage	Most Recent Renewal Date	Maximum Coverages			Maximum Assessments for Single Incidents
Public liability and nuclear worker liability:
American Nuclear Insurers	January 1, 2022	$	450		$	—
Pool participation	(a)	13,210		(a)	138		(b)
		$	13,660	(c)	$	138
Property damage:
NEIL and EMANI	April 1, 2022	$	3,200	(d)	$	26	(e)
Accidental outage:
NEIL	April 1, 2022	$	490	(f)	$	7	(e)

(a)Provided through mandatory participation in an industrywide retrospective premium assessment program. The maximum coverage available is dependent on the number of United States commercial reactors participating in the program.

(b)Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $450 million in the event of an incident at any licensed United States commercial reactor, payable at $21 million per year.

(c)Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. This limit is subject to change to account for the effects of inflation and changes in the number of licensed power reactors.

(d)NEIL provides $2.7 billion in property damage, stabilization, decontamination, and premature decommissioning insurance for radiation events and $2.3 billion in property damage insurance for nonradiation events. EMANI provides $490 million in property damage insurance for both radiation and nonradiation events.

(e)All NEIL-insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL.

(f)Accidental outage insurance provides for lost sales in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first 12 weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter for a total not exceeding the policy limit of $490 million. Nonradiation events are limited to $328 million.

Retirement Benefits (Tables)

9 Months Ended

Sep. 30, 2022

Retirement Benefits [Abstract]

Components Of Net Periodic Benefit Cost

The following table presents the components of the net periodic benefit cost (income) incurred for Ameren’s pension and postretirement benefit plans for the three and nine months ended September 30, 2022 and 2021:


	Pension Benefits								Postretirement Benefits
	Three Months				Nine Months				Three Months				Nine Months
	2022		2021		2022		2021		2022		2021		2022		2021
Service cost(a)	$	31	$	33	$	95	$	100	$	5	$	5	$	15	$	17
Non-service cost components:
Interest cost	42		38		123		114		8		9		25		25
Expected return on plan assets	(80)		(74)		(240)		(223)		(21)		(20)		(64)		(60)
Amortization of:

Prior service benefit	—		—		—		—		(1)		(1)		(3)		(3)
Actuarial loss (gain)	7		18		19		55		(5)		(1)		(14)		(4)
Total non-service cost components(b)	$	(31)	$	(18)	$	(98)	$	(54)	$	(19)	$	(13)	$	(56)	$	(42)

Net periodic benefit cost (income)(c)	$	—	$	15	$	(3)	$	46	$	(14)	$	(8)	$	(41)	$	(25)

(a)Service cost, net of capitalization, is reflected in “Operating Expenses – Other operations and maintenance” on Ameren’s statement of income.

(b)Non-service cost components are reflected in “Other Income, Net” on Ameren’s statement of income. See Note 5 – Other Income, Net, for additional information.

(c)Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.

Summary Of Benefit Plan Costs Incurred

Ameren Missouri and Ameren Illinois are responsible for their respective share of Ameren’s pension and other postretirement costs. The following table presents the respective share of net periodic pension and other postretirement benefit costs (income) incurred for the three and nine months ended September 30, 2022 and 2021:


	Pension Benefits								Postretirement Benefits
	Three Months				Nine Months				Three Months				Nine Months
	2022		2021		2022		2021		2022		2021		2022		2021
Ameren Missouri(a)	$	—	$	7	$	(2)	$	22	$	(3)	$	(1)	$	(10)	$	(3)
Ameren Illinois	1		8		2		25		(11)		(8)		(31)		(23)
Other	(1)		—		(3)		(1)		—		1		—		1
Ameren(a)	$	—	$	15	$	(3)	$	46	$	(14)	$	(8)	$	(41)	$	(25)

(a)Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.

Income Taxes Income Taxes (Tables)

9 Months Ended

Sep. 30, 2022

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation

The following table presents a reconciliation of the federal statutory corporate income tax rate to the effective income tax rate for the three and nine months ended September 30, 2022 and 2021:


	Ameren				Ameren Missouri				Ameren Illinois
	2022		2021		2022		2021		2022		2021
Three Months
Federal statutory corporate income tax rate	21	%	21	%	21	%	21	%	21	%	21	%
Increases (decreases) from:
Amortization of deferred investment tax credit	—		(1)		(1)		(1)		—		—
Amortization of excess deferred taxes(a)	(8)		(8)		(15)		(17)		(2)		(2)
Depreciation differences	—		—		—		—		—		(1)

Renewable and other tax credits(b)	(4)		(2)		(10)		(8)		—		—
State tax	4		4		3		4		7		7
Stock-based compensation	1		—		—		—		—		—
Cash surrender value of COLI	1		—		—		—		—		—
Effective income tax rate	15	%	14	%	(2)	%	(1)	%	26	%	25	%
Nine Months
Federal statutory corporate income tax rate	21	%	21	%	21	%	21	%	21	%	21	%
Increases (decreases) from:
Amortization of deferred investment tax credit	—		—		(1)		—		—		—
Amortization of excess deferred taxes(a)	(8)		(9)		(15)		(17)		(2)		(3)


Renewable and other tax credits(b)	(4)		(3)		(10)		(8)		—		—
State tax	5		5		3		3		7		7
Stock-based compensation	—		(1)		—		—		—		—
Effective income tax rate	14	%	13	%	(2)	%	(1)	%	26	%	25	%

(a)Reflects the amortization of amounts resulting from the revaluation of deferred income taxes subject to regulatory ratemaking, which are being refunded to customers. Deferred income taxes are revalued when federal or state income tax rates change, and the offset to the revaluation of deferred income taxes subject to regulatory ratemaking is recorded to a regulatory asset or liability.

(b)Includes credits associated with the High Prairie and Atchison renewable energy centers. Ameren Missouri placed the High Prairie Renewable Energy Center in service in December 2020. Additionally, Ameren Missouri placed in service the wind turbines at its Atchison Renewable Energy Center throughout the first half of 2021. The benefit of the credits associated with Missouri renewable energy standard compliance is refunded to customers through the RESRAM.

Supplemental Information (Tables)

9 Months Ended

Sep. 30, 2022

Supplemental Information [Abstract]

Schedule of Cash and Cash Equivalents Including Restricted Cash

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets and the statements of cash flows at September 30, 2022, and December 31, 2021:


	September 30, 2022						December 31, 2021
	Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois
“Cash and cash equivalents”	$	7	$	—	$	—	$	8	$	—	$	—

Restricted cash included in “Other current assets”	7		3		4		16		4		6
Restricted cash included in “Other assets”	162		—		162		127		—		127
Restricted cash included in “Nuclear decommissioning trust fund”	4		4		—		4		4		—
Total cash, cash equivalents, and restricted cash	$	180	$	7	$	166	$	155	$	8	$	133

Schedule of Accounts, Notes, Loans and Financing Receivable

The following table provides a reconciliation of the beginning and ending amount of the allowance for doubtful accounts for the three and nine months ended September 30, 2022 and 2021:


	Three Months				Nine Months
	2022		2021		2022		2021
Ameren:
Beginning of period	$	30	$	42	$	29	$	50
Bad debt expense	15		7		26		8
Net write-offs	(14)		(13)		(24)		(22)
End of period	$	31	$	36	$	31	$	36
Ameren Missouri:
Beginning of period	$	12	$	16	$	13	$	16
Bad debt expense	3		2		6		5
Net write-offs	(3)		(4)		(7)		(7)
End of period	$	12	$	14	$	12	$	14
Ameren Illinois:(a)
Beginning of period	$	18	$	26	$	16	$	34
Bad debt expense	12		5		20		3		(b)
Net write-offs	(11)		(9)		(17)		(15)
End of period	$	19	$	22	$	19	$	22

(a)Ameren Illinois has rate-adjustment mechanisms that allow it to recover the difference between its actual net bad debt write-offs under GAAP, including those associated with receivables purchased from alternative retail electric suppliers, and the amount of net bad debt write-offs included in its base rates.

(b)In the nine months ended September 30, 2021, Ameren Illinois’ bad debt expense was reduced as a result of state funding received for customer bill assistance.

Schedule of Cash Flow, Supplemental Disclosures

The following table provides noncash financing and investing activity excluded from the statements of cash flows for the nine months ended September 30, 2022 and 2021:


	September 30, 2022						September 30, 2021
	Ameren		Ameren Missouri				Ameren Illinois	Ameren		Ameren Missouri		Ameren Illinois
Investing
Accrued capital expenditures	$	367	$	187	$	180		$	396	$	209	$	182

Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund	(262)		(262)		—			85		85		—
Financing
Issuance of common stock for stock-based compensation	$	31	$	—	$	—		$	33	$	—	$	—
Issuance of common stock under the DRPlus	8		—		—			—		—		—

Asset Retirement Obligation Disclosure

The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the nine months ended September 30, 2022:


	Ameren Missouri			Ameren Illinois			Ameren
Balance at December 31, 2021	$	760	(a)	$	4	(b)	$	764	(a)
Liabilities incurred	1			—			1
Liabilities settled	(3)			—			(3)
Accretion	23		(c)	—			23		(c)
Change in estimates	(7)			—			(7)
Balance at September 30, 2022	$	774	(a)	$	4	(b)	$	778	(a)

(a)Balance included $7 million in “Other current liabilities” on the balance sheet as of both September 30, 2022, and December 31, 2021.

(b)Included in “Other deferred credits and liabilities” on the balance sheet.

(c)Accretion expense attributable to Ameren Missouri was recorded as a decrease to regulatory liabilities.

Schedule of excise taxes

The following table presents the excise taxes recorded on a gross basis in “Operating Revenues – Electric,” “Operating Revenues – Natural gas” and “Operating Expenses – Taxes other than income taxes” on the statements of income for the three and nine months ended September 30, 2022 and 2021:


	Three Months				Nine Months
	2022		2021		2022		2021
Ameren Missouri	$	55	$	54	$	128	$	120
Ameren Illinois	28		27		101		93
Ameren	$	83	$	81	$	229	$	213

Schedule of Earnings Per Share, Basic and Diluted

The following table reconciles the basic weighted-average number of common shares outstanding to the diluted weighted-average number of common shares outstanding for the three and nine months ended September 30, 2022 and 2021:


	Three Months		Nine Months
	2022	2021	2022	2021


Weighted-average Common Shares Outstanding – Basic	258.4	257.3	258.2	255.9
Assumed settlement of performance share units and restricted stock units	0.9	1.3	1.0	1.3
Dilutive effect of forward sale agreements	0.2	—	0.1	—
Weighted-average Common Shares Outstanding – Diluted(a)	259.5	258.6	259.3	257.2

(a)There was an immaterial number of anti-dilutive securities excluded from the earnings per diluted share calculations for the three and nine months ended September 30, 2022 and 2021.

Segment Information (Tables)

9 Months Ended

Sep. 30, 2022

Segment Reporting [Abstract]

Schedule Of Segment Reporting Information By Segment

The following tables present revenues, net income attributable to common shareholders, and capital expenditures by segment at Ameren and Ameren Illinois for the three and nine months ended September 30, 2022 and 2021. Ameren, Ameren Missouri, and Ameren Illinois management review segment capital expenditure information rather than any individual or total asset amount. For additional information about our segments, see Note 16 – Segment Information under Part II, Item 8, of the Form 10-K.

Ameren


	Ameren Missouri			Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission			Other		Intersegment Eliminations		Ameren
Three Months 2022:
External revenues	$	1,351		$	672	$	146	$	137		$	—	$	—	$	2,306
Intersegment revenues	8			—		—		32			—		(40)		—
Net income (loss) attributable to Ameren common shareholders	397			51		(4)		78		(a)	(70)		—		452
Capital expenditures	431			163		114		187			1		3		899
Three Months 2021:
External revenues	$	1,118		$	425	$	127	$	141		$	—	$	—	$	1,811
Intersegment revenues	11			3		—		19			—		(33)		—
Net income (loss) attributable to Ameren common shareholders	375			36		(8)		73		(a)	(51)		—		425
Capital expenditures	466		(b)	143		93		154			2		(8)		850		(b)
Nine Months 2022:
External revenues	$	3,071		$	1,640	$	811	$	389		$	—	$	—	$	5,911
Intersegment revenues	25			1		—		76			—		(102)		—
Net income (loss) attributable to Ameren common shareholders	547			151		82		199		(a)	(68)		—		911
Capital expenditures	1,237			444		232		519			4		1		2,437
Nine Months 2021:
External revenues	$	2,612		$	1,222	$	642	$	373		$	—	$	—	$	4,849
Intersegment revenues	30			5		—		53			—		(88)		—
Net income (loss) attributable to Ameren common shareholders	533			123		75		175		(a)	(41)		—		865
Capital expenditures	1,567		(b)	429		202		426			3		(14)		2,613		(b)

(a)Ameren Transmission earnings reflect an allocation of financing costs from Ameren (parent).

(b)Includes $98 million and $515 million at Ameren and Ameren Missouri for wind generation expenditures for the three and nine months ended September 30, 2021, respectively.

Ameren Illinois


	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Intersegment Eliminations		Ameren Illinois
Three Months 2022:
External revenues	$	672	$	146	$	86	$	—	$	904
Intersegment revenues	—		—		31		(31)		—
Net income (loss) available to common shareholder	51		(4)		56		—		103
Capital expenditures	163		114		169		—		446
Three Months 2021:
External revenues	$	428	$	127	$	90	$	—	$	645
Intersegment revenues	—		—		18		(18)		—
Net income (loss) available to common shareholder	36		(8)		51		—		79
Capital expenditures	143		93		144		—		380


	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Intersegment Eliminations		Ameren Illinois
Nine Months 2022:
External revenues	$	1,641	$	811	$	245	$	—	$	2,697
Intersegment revenues	—		—		75		(75)		—
Net income available to common shareholder	151		82		142		—		375
Capital expenditures	444		232		469		—		1,145
Nine Months 2021:
External revenues	$	1,227	$	642	$	228	$	—	$	2,097
Intersegment revenues	—		—		49		(49)		—
Net income available to common shareholder	123		75		116		—		314
Capital expenditures	429		202		395		—		1,026

Disaggregation of Revenue

The following tables present disaggregated revenues by segment at Ameren and Ameren Illinois for the three and nine months ended September 30, 2022 and 2021. Economic factors affect the nature, timing, amount, and uncertainty of revenues and cash flows in a similar manner across customer classes. Revenues from alternative revenue programs have a similar distribution among customer classes as revenues from contracts with customers. Other revenues not associated with contracts with customers are presented in the Other customer classification, along with electric transmission and off-system revenues.

Ameren


	Ameren Missouri		Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission		Intersegment Eliminations		Ameren
Three Months 2022:
Residential	$	564	$	407	$	—	$	—	$	—	$	971
Commercial	430		233		—		—		—		663
Industrial	99		47		—		—		—		146
Other	245		(15)		—		169		(39)		360
Total electric revenues	$	1,338	$	672	$	—	$	169	$	(39)	$	2,140
Residential	$	11	$	—	$	89	$	—	$	—	$	100
Commercial	6		—		25		—		—		31
Industrial	1		—		5		—		—		6
Other	3		—		27		—		(1)		29
Total natural gas revenues	$	21	$	—	$	146	$	—	$	(1)	$	166
Total revenues(a)	$	1,359	$	672	$	146	$	169	$	(40)	$	2,306
Three Months 2021:
Residential	$	537	$	258	$	—	$	—	$	—	$	795
Commercial	412		143		—		—		—		555
Industrial	98		26		—		—		—		124
Other	66		1		—		160		(33)		194
Total electric revenues	$	1,113	$	428	$	—	$	160	$	(33)	$	1,668
Residential	$	9	$	—	$	75	$	—	$	—	$	84
Commercial	4		—		23		—		—		27
Industrial	—		—		3		—		—		3
Other	3		—		26		—		—		29
Total natural gas revenues	$	16	$	—	$	127	$	—	$	—	$	143
Total revenues(a)	$	1,129	$	428	$	127	$	160	$	(33)	$	1,811


	Ameren Missouri		Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission		Intersegment Eliminations		Ameren
Nine Months 2022:
Residential	$	1,267	$	954	$	—	$	—	$	—	$	2,221
Commercial	968		571		—		—		—		1,539
Industrial	229		145		—		—		—		374
Other	502		(29)		—		465		(101)		837
Total electric revenues	$	2,966	$	1,641	$	—	$	465	$	(101)	$	4,971
Residential	$	78	$	—	$	575	$	—	$	—	$	653
Commercial	36		—		152		—		—		188
Industrial	4		—		33		—		—		37
Other	12		—		51		—		(1)		62
Total natural gas revenues	$	130	$	—	$	811	$	—	$	(1)	$	940
Total revenues(a)	$	3,096	$	1,641	$	811	$	465	$	(102)	$	5,911
Nine Months 2021:
Residential	$	1,177	$	705	$	—	$	—	$	—	$	1,882
Commercial	899		402		—		—		—		1,301
Industrial	221		94		—		—		—		315
Other	246		26		—		426		(88)		610
Total electric revenues	$	2,543	$	1,227	$	—	$	426	$	(88)	$	4,108
Residential	$	54	$	—	$	438	$	—	$	—	$	492
Commercial	23		—		116		—		—		139
Industrial	2		—		20		—		—		22
Other	20		—		68		—		—		88
Total natural gas revenues	$	99	$	—	$	642	$	—	$	—	$	741
Total revenues(a)	$	2,642	$	1,227	$	642	$	426	$	(88)	$	4,849

(a)The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the three and nine months ended September 30, 2022 and 2021:


	Ameren Missouri			Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Transmission		Ameren
Three Months 2022:
Revenues from alternative revenue programs	$	14		$	(83)	$	(3)	$	(11)	$	(83)
Other revenues not from contracts with customers	(45)		(a)	2		—		—		(43)		(a)
Three Months 2021:
Revenues from alternative revenue programs	$	6		$	(97)	$	(5)	$	1	$	(95)
Other revenues not from contracts with customers	7		(b)	6		—		—		13		(b)
Nine Months 2022:
Revenues from alternative revenue programs	$	8		$	13	$	(5)	$	(14)	$	2
Other revenues not from contracts with customers	(81)		(a), (b)	5		2		—		(74)		(a), (b)
Nine Months 2021:
Revenues from alternative revenue programs	$	(9)		$	(2)	$	—	$	5	$	(6)
Other revenues not from contracts with customers	71		(b)	9		2		—		82		(b)

(a)Includes net realized losses on derivative power contracts.

(b)Includes insurance recoveries related to lost sales associated with the Callaway Energy Center maintenance outage. See Note 9 – Callaway Energy Center under Part II, Item 8, of the Form 10-K for additional information.

Ameren Illinois


	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Intersegment Eliminations		Ameren Illinois
Three Months 2022:
Residential	$	407	$	89	$	—	$	—	$	496
Commercial	233		25		—		—		258
Industrial	47		5		—		—		52
Other	(15)		27		117		(31)		98
Total revenues(a)	$	672	$	146	$	117	$	(31)	$	904
Three Months 2021:
Residential	$	258	$	75	$	—	$	—	$	333
Commercial	143		23		—		—		166
Industrial	26		3		—		—		29
Other	1		26		108		(18)		117
Total revenues(a)	$	428	$	127	$	108	$	(18)	$	645
Nine Months 2022:
Residential	$	954	$	575	$	—	$	—	$	1,529
Commercial	571		152		—		—		723
Industrial	145		33		—		—		178
Other	(29)		51		320		(75)		267
Total revenues(a)	$	1,641	$	811	$	320	$	(75)	$	2,697
Nine Months 2021:
Residential	$	705	$	438	$	—	$	—	$	1,143
Commercial	402		116		—		—		518
Industrial	94		20		—		—		114
Other	26		68		277		(49)		322
Total revenues(a)	$	1,227	$	642	$	277	$	(49)	$	2,097

(a)The following table presents increases/(decreases) in revenues from alternative revenue programs and other revenues not from contracts with customers for the Ameren Illinois segments for the three and nine months ended September 30, 2022 and 2021:


	Ameren Illinois Electric Distribution		Ameren Illinois Natural Gas		Ameren Illinois Transmission		Ameren Illinois
Three Months 2022:
Revenues from alternative revenue programs	$	(83)	$	(3)	$	(10)	$	(96)
Other revenues not from contracts with customers	2		—		—		2

Three Months 2021:
Revenues from alternative revenue programs	$	(97)	$	(5)	$	3	$	(99)
Other revenues not from contracts with customers	6		—		—		6

Nine Months 2022:
Revenues from alternative revenue programs	$	13	$	(5)	$	(12)	$	(4)
Other revenues not from contracts with customers	5		2		—		7

Nine Months 2021:
Revenues from alternative revenue programs	$	(2)	$	—	$	4	$	2
Other revenues not from contracts with customers	9		2		—		11

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Basis Of Presentation And Significant Accounting Policies [Line Items]
Unconsolidated variable interest	$ 58	$ 56
Cash Surrender Value of Life Insurance	239	278
Corporate owned life insurance, borrowings	108	109
Ameren Illinois Company
Basis Of Presentation And Significant Accounting Policies [Line Items]
Cash Surrender Value of Life Insurance	116	117
Corporate owned life insurance, borrowings	108	$ 109
Partnership Funding Commitment
Basis Of Presentation And Significant Accounting Policies [Line Items]
Outstanding funding commitments	$ 21

Rate And Regulatory Matters (Narrative-Missouri) (Details) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2022 USD ($)	Jun. 30, 2022 MWh	Mar. 31, 2022 MWh	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) numberOfCountriesInvestigatedByTheDOC	Sep. 30, 2021 USD ($)
Rate And Regulatory Matters [Line Items]
Revenues	$ 2,306			$ 1,811	$ 5,911	$ 4,849
Union Electric Company
Rate And Regulatory Matters [Line Items]
Missouri Renewable Energy Standard Percentage					15.00%
Missouri Renewable Energy Standard Percentage - Solar					2.00%
Number of Countries Investigated by the DOC \| numberOfCountriesInvestigatedByTheDOC					4
Union Electric Company \| Pending Rate Case \| Electric
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 316
Public Utilities, Requested Return on Equity, Percentage					10.20%
Public Utilities, Requested Equity Capital Structure, Percentage					51.90%
Rate Base					$ 11,600
Months to complete a rate proceeding					11 months
Union Electric Company \| Wind Generation Facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh		200	150
Union Electric Company \| Final Rate Order \| Electric \| MEEIA 2019 [Domain]
Rate And Regulatory Matters [Line Items]
Revenues	$ 12			$ 9
Union Electric Company \| Maximum
Rate And Regulatory Matters [Line Items]
PISA Rate Increase Limit Beginning 2024					2.50%
Public Utilities, Approved Rate Increase (Decrease), Percentage					2.85%
Percentage of energy sourced from renewable resources					100.00%

Rate And Regulatory Matters (Narrative-Illinois) (Details) - Ameren Illinois Company $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($) numberOfProposedPerformanceMetrics
Rate And Regulatory Matters [Line Items]
Annual investment in energy-efficiency programs	$ 120
Minimum
Rate And Regulatory Matters [Line Items]
ICC required RTO cost benefit study duration	5 years
Maximum
Rate And Regulatory Matters [Line Items]
ICC required RTO cost benefit study duration	10 years
Electric Distribution
Rate And Regulatory Matters [Line Items]
Requested Return on Equity Adjustment	0.24%
Number of Proposed Performance Metrics \| numberOfProposedPerformanceMetrics	7
Electric Distribution \| Minimum
Rate And Regulatory Matters [Line Items]
Return on equity adjustment	0.20%
Electric Distribution \| Maximum
Rate And Regulatory Matters [Line Items]
Return on equity adjustment	0.60%
Pending Rate Case \| Electric Distribution \| IEIMA
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 84
Public Utilities, Requested Equity Capital Structure, Percentage	54.00%
ICC Staff Recommended Rate Increase (Decrease)	$ 61
ICC Staff Recommended Equity Capital Structure, Percentage	50.00%
Pending Rate Case \| Electric Distribution \| FEJA energy-efficiency rider
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 17
ICC Staff Recommended Rate Increase (Decrease)	15
Pending Rate Case \| Natural gas
Rate And Regulatory Matters [Line Items]
Natural Gas Capital Investment Prudency Challenge	70
Challenged Recoveries Under the QIP	3
IETL
Rate And Regulatory Matters [Line Items]
Energy Transition Assistance Fund Surcharge	$ 50

Rate And Regulatory Matters (Narrative-Federal) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2020	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Rate And Regulatory Matters [Line Items]
Regulatory liabilities		$ 5,658		$ 5,658		$ 5,848
Revenues		2,306	$ 1,811	5,911	$ 4,849
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Regulatory liabilities		2,532		2,532		$ 2,374
Revenues		904	$ 645	2,697	$ 2,097
Final Rate Order \| Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Regulatory liabilities		$ 9		9
Midwest Independent Transmission System Operator, Inc
Rate And Regulatory Matters [Line Items]
Revenues				17
Midwest Independent Transmission System Operator, Inc \| Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Revenues				$ 11
Midwest Independent Transmission System Operator, Inc \| Final Rate Order
Rate And Regulatory Matters [Line Items]
Approved return on equity percentage	10.02%

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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+ Details

Short-Term Debt And Liquidity (Narrative) (Details) $ in Billions	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021	Sep. 30, 2022 USD ($)	Sep. 30, 2021
Credit Agreements
Short-term Debt [Line Items]
Net Liquidity Available	$ 1.1		$ 1.1
Actual debt-to-capital ratio	0.59		0.59
Utilities
Short-term Debt [Line Items]
Short-term Debt, Weighted Average Interest Rate, over Time	2.48%	0.06%	1.29%	0.17%
Union Electric Company \| Missouri Credit Agreement
Short-term Debt [Line Items]
Actual debt-to-capital ratio	0.49		0.49
Ameren Illinois Company \| Illinois Credit Agreement
Short-term Debt [Line Items]
Actual debt-to-capital ratio	0.45		0.45

Short-Term Debt and Liquidity (Short-Term Debt outstanding) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Short-term Debt [Line Items]
Short-term debt	$ 1,221	$ 545
Union Electric Company
Short-term Debt [Line Items]
Short-term debt	178	165
Ameren Illinois Company
Short-term Debt [Line Items]
Short-term debt	353	103
Commercial Paper
Short-term Debt [Line Items]
Short-term debt	1,221	545
Commercial Paper \| Parent Company
Short-term Debt [Line Items]
Short-term debt	690	277
Commercial Paper \| Union Electric Company
Short-term Debt [Line Items]
Short-term debt	178	165
Commercial Paper \| Ameren Illinois Company
Short-term Debt [Line Items]
Short-term debt	$ 353	$ 103

Short-Term Debt and Liquidity (Short-Term Debt Activity) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Short-term Debt [Line Items]
Average daily amount outstanding	$ 791	$ 665
Weighted-average interest rate	1.47%	0.22%
Short-term Debt, Maximum Amount Outstanding During Period	$ 1,222	$ 1,134
Peak interest rate	3.60%	0.33%
Parent Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 439	$ 404
Weighted-average interest rate	1.58%	0.23%
Short-term Debt, Maximum Amount Outstanding During Period	$ 690	$ 650
Peak interest rate	3.55%	0.33%
Union Electric Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 253	$ 121
Weighted-average interest rate	1.16%	0.22%
Short-term Debt, Maximum Amount Outstanding During Period	$ 539	$ 546
Peak interest rate	3.55%	0.25%
Ameren Illinois Company
Short-term Debt [Line Items]
Average daily amount outstanding	$ 99	$ 140
Weighted-average interest rate	1.77%	0.22%
Short-term Debt, Maximum Amount Outstanding During Period	$ 354	$ 485
Peak interest rate	3.60%	0.25%

Long-Term debt and Equity Financings (Details) $ / shares in Units, shares in Millions	1 Months Ended		3 Months Ended			9 Months Ended
	Aug. 31, 2022 USD ($)	Apr. 30, 2022 USD ($)	Sep. 30, 2022 USD ($) shares	Mar. 31, 2022 USD ($) shares	Sep. 30, 2021 shares	Sep. 30, 2022 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) shares	Aug. 29, 2022 USD ($)	May 31, 2021 USD ($)
Long-Term Debt And Equity Financings [Line Items]
Shares issued under the DRPlus and 401(k) plan \| shares			0.1		0.1	0.4	0.4
Issuances of common stock						$ 29,000,000	$ 297,000,000
Stock Issued During Period, Shares, Other \| shares			0.0	0.4	0.0	0.4	0.5
Stock Issued During Period, Value, Other				$ 31,000,000
Maximum Value Of Shares To Be Issued Under ATM Program									$ 750,000,000
Forward Contract Indexed to Issuer's Equity, Basis Spread			75			75
Minimum
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share \| $ / shares						$ 86.35
Maximum
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share \| $ / shares						94.80
Weighted Average
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share \| $ / shares						$ 90.31
Dividend reinvestment and 401 (k) plans
Long-Term Debt And Equity Financings [Line Items]
Issuances of common stock			$ 4,000,000			$ 29,000,000
Accrued Proceeds from Issuance of Common Stock						$ 8,000,000
Forward Sale Agreements Outstanding
Long-Term Debt And Equity Financings [Line Items]
Forward Contract Indexed to Issuer's Equity, Indexed Shares (in shares) \| shares			6.6			6.6
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value \| shares			6.6			6.6
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value			$ 587,000,000			$ 587,000,000
Period End Net Cash Settlement Price			58,000,000			58,000,000
Period End Net Share Settlement Price			700,000			700,000
Forward Sale Agreement Equity Offering Shares			6,600,000			6,600,000
Forward Sale Agreement Gross Sales Price			600,000,000			600,000,000
Forward Sale Agreement, Compensation Received by Counterparty			$ 6,000,000			$ 6,000,000
Union Electric Company \| Secured Debt \| Senior Secured Notes 3.90% Due 2052
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount		$ 525,000,000
Debt Instrument, Interest Rate, Stated Percentage		3.90%
Proceeds from Issuance of Secured Debt		$ 519,000,000
Ameren Illinois Company \| Unsecured Debt \| Senior Secured Notes 3.85% Due 2032
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount								$ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage								3.85%
Proceeds from Issuance of Secured Debt	$ 496,000,000
Ameren Illinois Company \| Unsecured Debt \| Senior Secured Notes 2.70% Due 2022
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount								$ 400,000,000
Debt Instrument, Interest Rate, Stated Percentage								2.70%
Ameren Transmission Company of Illinois \| Unsecured Debt \| Senior Unsecured Notes, 2.96%, Due 2052
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Face Amount								$ 95,000,000
Debt Instrument, Interest Rate, Stated Percentage			2.96%			2.96%
Proceeds from Issuance of Debt	$ 95,000,000
Ameren Transmission Company of Illinois \| Unsecured Debt \| Senior Unsecured Notes, 3.43%, Due 2050
Long-Term Debt And Equity Financings [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.43%			3.43%
Long-Term Debt, Maturity, Year One			$ 50,000,000			$ 50,000,000

Other Income, Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Other Income, Net (Details) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	$ 12	$ 14	$ 31	$ 30
Interest income on industrial development revenue bonds	6	7	18	19
Non-service cost components of net periodic benefit income	45	34	138	102
Miscellaneous income	5	1	14	7
Income (Loss) from Equity Method Investments	(3)	2	1	8
Donations	(1)	(1)	(5)	(5)
Miscellaneous expense	(6)	(1)	(17)	(10)
Total Other Income, Net	58	56	180	151
Union Electric Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	7	7	17	17
Interest income on industrial development revenue bonds	6	7	18	19
Non-service cost components of net periodic benefit income	13	13	41	41
Miscellaneous income	2	2	5	3
Donations	0	0	(2)	(1)
Miscellaneous expense	(3)	(2)	(7)	(5)
Total Other Income, Net	25	27	72	74
Defined Benefit Plan, Non-service Cost or Income Components - Tracker	5	(3)	16	(6)
Ameren Illinois Company
Other Nonoperating Income (Expense) [Line Items]
Allowance for equity funds used during construction	5	7	14	13
Non-service cost components of net periodic benefit income	21	13	63	41
Miscellaneous income	4	0	9	4
Donations	(1)	(1)	(3)	(4)
Miscellaneous expense	(3)	0	(8)	(5)
Total Other Income, Net	$ 26	$ 19	$ 75	$ 49

Derivative Financial Instruments (Open Gross Derivative Volumes By Commodity Type) (Detail) lb in Thousands, gal in Millions, MWh in Millions, MMBTU in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2022 MWh MMBTU lb gal	Dec. 31, 2021 MMBTU MWh lb gal
Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	19	30
Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	187	179
Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	8	12
Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	406	586
Union Electric Company \| Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	19	30
Union Electric Company \| Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	43	35
Union Electric Company \| Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	2	6
Union Electric Company \| Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	406	586
Ameren Illinois Company \| Fuel oils
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume \| gal	0	0
Ameren Illinois Company \| Natural gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	144	144
Ameren Illinois Company \| Power
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	6	6
Ameren Illinois Company \| Uranium
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Mass \| lb	0	0

Derivative Financial Instruments (Derivative Instruments Carrying Value) (Detail) - Not Designated As Hedging Instrument - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Derivative assets	$ 167	$ 90
Derivative Liability	177	202
Fuel oils \| Other current assets
Derivative [Line Items]
Derivative assets	12	8
Fuel oils \| Other assets
Derivative [Line Items]
Derivative assets	3	5
Fuel oils \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	1	0
Natural gas \| Other current assets
Derivative [Line Items]
Derivative assets	71	35
Natural gas \| Other assets
Derivative [Line Items]
Derivative assets	34	18
Natural gas \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	4	3
Natural gas \| Other current liabilities
Derivative [Line Items]
Derivative Liability	11	8
Power \| Other current assets
Derivative [Line Items]
Derivative assets	39	23
Power \| Other assets
Derivative [Line Items]
Derivative assets	5	0
Power \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	50	131
Power \| Other current liabilities
Derivative [Line Items]
Derivative Liability	111	59
Uranium \| Other current assets
Derivative [Line Items]
Derivative assets	2	0
Uranium \| Other assets
Derivative [Line Items]
Derivative assets	1	1
Uranium \| Other current liabilities
Derivative [Line Items]
Derivative Liability	0	1
Union Electric Company
Derivative [Line Items]
Derivative assets	73	49
Derivative Liability	129	77
Union Electric Company \| Fuel oils \| Other current assets
Derivative [Line Items]
Derivative assets	12	8
Union Electric Company \| Fuel oils \| Other assets
Derivative [Line Items]
Derivative assets	3	5
Union Electric Company \| Fuel oils \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	1	0
Union Electric Company \| Natural gas \| Other current assets
Derivative [Line Items]
Derivative assets	14	7
Union Electric Company \| Natural gas \| Other assets
Derivative [Line Items]
Derivative assets	13	5
Union Electric Company \| Natural gas \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	1	1
Union Electric Company \| Natural gas \| Mark-to-market derivative liabilities
Derivative [Line Items]
Derivative Liability	2	2
Union Electric Company \| Natural gas \| Other current liabilities
Derivative [Line Items]
Derivative Liability	0	0
Union Electric Company \| Power \| Other current assets
Derivative [Line Items]
Derivative assets	28	23
Union Electric Company \| Power \| Other assets
Derivative [Line Items]
Derivative assets	0	0
Union Electric Company \| Power \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	14	23
Union Electric Company \| Power \| Mark-to-market derivative liabilities
Derivative [Line Items]
Derivative Liability	111	50
Union Electric Company \| Power \| Other current liabilities
Derivative [Line Items]
Derivative Liability	0	0
Union Electric Company \| Uranium \| Other current assets
Derivative [Line Items]
Derivative assets	2	0
Union Electric Company \| Uranium \| Other assets
Derivative [Line Items]
Derivative assets	1	1
Union Electric Company \| Uranium \| Mark-to-market derivative liabilities
Derivative [Line Items]
Derivative Liability	0	1
Union Electric Company \| Uranium \| Other current liabilities
Derivative [Line Items]
Derivative Liability	0	0
Ameren Illinois Company
Derivative [Line Items]
Derivative assets	94	41
Derivative Liability	48	125
Ameren Illinois Company \| Fuel oils \| Other current assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company \| Fuel oils \| Other assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company \| Fuel oils \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	0	0
Ameren Illinois Company \| Natural gas \| Other current assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company \| Natural gas \| Other assets
Derivative [Line Items]
Derivative assets	21	13
Ameren Illinois Company \| Natural gas \| Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	57	28
Ameren Illinois Company \| Natural gas \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	3	2
Ameren Illinois Company \| Natural gas \| Other current liabilities
Derivative [Line Items]
Derivative Liability	9	6
Ameren Illinois Company \| Power \| Other current assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company \| Power \| Other assets
Derivative [Line Items]
Derivative assets	5	0
Ameren Illinois Company \| Power \| Mark-to-market derivative assets
Derivative [Line Items]
Derivative assets	11	0
Ameren Illinois Company \| Power \| Other deferred credits and liabilities
Derivative [Line Items]
Derivative Liability	36	108
Ameren Illinois Company \| Power \| Other current liabilities
Derivative [Line Items]
Derivative Liability	0	9
Ameren Illinois Company \| Uranium \| Other current assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company \| Uranium \| Other assets
Derivative [Line Items]
Derivative assets	0	0
Ameren Illinois Company \| Uranium \| Other current liabilities
Derivative [Line Items]
Derivative Liability	$ 0	$ 0

Derivative Financial Instruments (Offsetting Assets and Liabilities) (Details) - Not Designated As Hedging Instrument - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	$ 167	$ 90
Gross derivative instruments not offset in the balance sheet	31	19
Gross cash collateral received not offset in the balance sheet	3	0
Net derivative asset	133	71
Gross derivative liability amount recognized on the balance sheet	177	202
Gross derivative instruments not offset in the balance sheet	31	19
Gross cash collateral posted not offset in the balance sheet	99	47
Net derivative liability	47	136
Union Electric Company
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	73	49
Gross derivative instruments not offset in the balance sheet	18	15
Gross cash collateral received not offset in the balance sheet	2	0
Net derivative asset	53	34
Gross derivative liability amount recognized on the balance sheet	129	77
Gross derivative instruments not offset in the balance sheet	18	15
Gross cash collateral posted not offset in the balance sheet	99	47
Net derivative liability	12	15
Ameren Illinois Company
Derivative [Line Items]
Gross derivative asset amount recognized on the balance sheet	94	41
Gross derivative instruments not offset in the balance sheet	13	4
Gross cash collateral received not offset in the balance sheet	1	0
Net derivative asset	80	37
Gross derivative liability amount recognized on the balance sheet	48	125
Gross derivative instruments not offset in the balance sheet	13	4
Gross cash collateral posted not offset in the balance sheet	0	0
Net derivative liability	$ 35	$ 121

Derivative Financial Instruments (Credit Risk) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($)
Credit Derivatives [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	$ 142
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	124
Union Electric Company
Credit Derivatives [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	55
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	43
Ameren Illinois Company
Credit Derivatives [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	87
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure	$ 81

Fair Value Measurements (Schedule Of Fair Value Hierarchy Of Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	$ 901	$ 1,152
Assets fair value	1,068	1,242
Excluded receivables, payables, and accrued income, net	9	7
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	574	824
Assets fair value	603	848
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	327	328
Assets fair value	418	373
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Assets fair value	47	21
Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	167	90
Derivative Liability	177	202
Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	29	24
Derivative Liability	99	45
Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	91	45
Derivative Liability	8	7
Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	47	21
Derivative Liability	70	150
Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	901	1,152
Assets fair value	974	1,201
Union Electric Company \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	574	824
Assets fair value	597	847
Union Electric Company \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	327	328
Assets fair value	353	340
Union Electric Company \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Assets fair value	24	14
Union Electric Company \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	73	49
Derivative Liability	129	77
Union Electric Company \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	23	23
Derivative Liability	99	45
Union Electric Company \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	26	12
Derivative Liability	2	2
Union Electric Company \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	24	14
Derivative Liability	28	30
Union Electric Company \| Fuel oils \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	15	13
Derivative Liability	1	0
Union Electric Company \| Fuel oils \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	13	13
Derivative Liability	1	0
Union Electric Company \| Fuel oils \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Union Electric Company \| Fuel oils \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2	0
Derivative Liability	0	0
Union Electric Company \| Natural gas \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	27	12
Derivative Liability	3	3
Union Electric Company \| Natural gas \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	1	0
Derivative Liability	0	0
Union Electric Company \| Natural gas \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	26	12
Derivative Liability	2	2
Union Electric Company \| Natural gas \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	1	1
Union Electric Company \| Power \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	28	23
Derivative Liability	125	73
Union Electric Company \| Power \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	9	10
Derivative Liability	98	45
Union Electric Company \| Power \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Union Electric Company \| Power \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	19	13
Derivative Liability	27	28
Union Electric Company \| Uranium \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	1
Derivative Liability	0	1
Union Electric Company \| Uranium \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Union Electric Company \| Uranium \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Union Electric Company \| Uranium \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	3	1
Derivative Liability	0	1
Union Electric Company \| Equity securities: \| U.S. large capitalization
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	574	824
Union Electric Company \| Equity securities: \| U.S. large capitalization \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	574	824
Union Electric Company \| Equity securities: \| U.S. large capitalization \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company \| Equity securities: \| U.S. large capitalization \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company \| Debt securities: \| U.S. Treasury and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	148	141
Union Electric Company \| Debt securities: \| U.S. Treasury and agency securities \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company \| Debt securities: \| U.S. Treasury and agency securities \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	148	141
Union Electric Company \| Debt securities: \| U.S. Treasury and agency securities \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company \| Debt securities: \| Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	115	131
Union Electric Company \| Debt securities: \| Corporate bonds \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company \| Debt securities: \| Corporate bonds \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	115	131
Union Electric Company \| Debt securities: \| Corporate bonds \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company \| Debt securities: \| Other Debt Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	64	56
Union Electric Company \| Debt securities: \| Other Debt Securities \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Union Electric Company \| Debt securities: \| Other Debt Securities \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	64	56
Union Electric Company \| Debt securities: \| Other Debt Securities \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Nuclear decommissioning trust fund:	0	0
Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	94	41
Ameren Illinois Company \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	6	1
Ameren Illinois Company \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	65	33
Ameren Illinois Company \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	23	7
Ameren Illinois Company \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	48	125
Ameren Illinois Company \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	0	0
Ameren Illinois Company \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	6	5
Ameren Illinois Company \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability	42	120
Ameren Illinois Company \| Natural gas \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	78	41
Derivative Liability	12	8
Ameren Illinois Company \| Natural gas \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	6	1
Derivative Liability	0	0
Ameren Illinois Company \| Natural gas \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	65	33
Derivative Liability	6	5
Ameren Illinois Company \| Natural gas \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	7	7
Derivative Liability	6	3
Ameren Illinois Company \| Power \| Commodity Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	16	0
Derivative Liability	36	117
Ameren Illinois Company \| Power \| Commodity Contract \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Ameren Illinois Company \| Power \| Commodity Contract \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative Liability	0	0
Ameren Illinois Company \| Power \| Commodity Contract \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	16	0
Derivative Liability	$ 36	$ 117

Fair Value Measurements (Schedule Of Changes In The Fair Value Of Financial Assets And Liabilities Classified As Level Three In The Fair Value Hierarchy) (Details) - Power - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (80)	$ (171)	$ (132)	$ (196)
Included in regulatory assets/liabilities	20	3	49	21
Settlements, assets	32	1	55	8
Change in unrealized gains (losses) related to assets/liabilities held at period end	25	2	61	21
Ending balance	(28)	(167)	(28)	(167)
Union Electric Company
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(36)	(5)	(15)	2
Included in regulatory assets/liabilities	(10)	(16)	(56)	(22)
Settlements, assets	38		63
Settlement, liabilities		(2)		(3)
Change in unrealized gains (losses) related to assets/liabilities held at period end	(3)	(17)	(39)	(21)
Ending balance	(8)	(23)	(8)	(23)
Ameren Illinois Company
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(44)	(166)	(117)	(198)
Included in regulatory assets/liabilities	30	19	105	43
Settlements, assets		3		11
Settlement, liabilities	(6)		(8)
Change in unrealized gains (losses) related to assets/liabilities held at period end	28	19	100	42
Ending balance	$ (20)	$ (144)	$ (20)	$ (144)

Fair Value Measurements (Schedule Of Valuation Process And Unobservable Inputs) (Details) - Power $ in Millions	Sep. 30, 2022 USD ($) $ / MWh $ / MMBTU	Dec. 31, 2021 USD ($) $ / MWh $ / MMBTU
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative assets \| $	$ 35	$ 13
Derivative liabilities \| $	$ (63)	$ (145)
Commodity Forward Price \| Discounted cash flow \| Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	42	32
Commodity Forward Price \| Discounted cash flow \| Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	118	55
Commodity Forward Price \| Discounted cash flow \| Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	60	40
Nodal Basis \| Discounted cash flow \| Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	(15)	(14)
Nodal Basis \| Discounted cash flow \| Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	2	0
Nodal Basis \| Discounted cash flow \| Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input	(5)	(2)
Commodity Future Price \| Discounted cash flow \| Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input \| $ / MMBTU	0
Commodity Future Price \| Discounted cash flow \| Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input \| $ / MMBTU	1
Commodity Future Price \| Discounted cash flow \| Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Measurement input \| $ / MMBTU	0	0

Fair Value Measurements (Schedule Of Carrying Amounts And Estimated Fair Values Of Financial Assets and Liabilities) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	$ 180	$ 155	$ 145	$ 301
Short-term debt	1,221	545
Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8	11	145
Short-term debt	178	165
Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	166	133	$ 122	$ 147
Short-term debt	353	103
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	180	155
Investments in industrial development revenue bonds	248	248
Short-term debt	1,221	545
Long-term debt (including current portion)	13,732	13,067
Debt Issuance Costs, Net	99	94
Carrying Amount \| Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8
Investments in industrial development revenue bonds	248	248
Short-term debt	178	165
Long-term debt (including current portion)	6,140	5,619
Debt Issuance Costs, Net	42	38
Carrying Amount \| Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	166	133
Short-term debt	353	103
Long-term debt (including current portion)	4,489	4,392
Debt Issuance Costs, Net	41	39
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	180	155
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	1,221	545
Long-term Debt, Fair Value	11,939	14,521
Fair Value \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	180	155
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	1,221	545
Long-term Debt, Fair Value	11,493	13,930
Fair Value \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	446	591
Fair Value \| Union Electric Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	178	165
Long-term Debt, Fair Value	5,352	6,321
Fair Value \| Union Electric Company \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	7	8
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value \| Union Electric Company \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	248	248
Short-term Debt, Fair Value	178	165
Long-term Debt, Fair Value	5,352	6,321
Fair Value \| Union Electric Company \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Investments, Fair Value Disclosure	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value \| Ameren Illinois Company
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	166	133
Short-term Debt, Fair Value	353	103
Long-term Debt, Fair Value	3,868	4,971
Fair Value \| Ameren Illinois Company \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	166	133
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	0	0
Fair Value \| Ameren Illinois Company \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Short-term Debt, Fair Value	353	103
Long-term Debt, Fair Value	3,868	4,971
Fair Value \| Ameren Illinois Company \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash, cash equivalents, and restricted cash	0	0
Short-term Debt, Fair Value	0	0
Long-term Debt, Fair Value	$ 0	$ 0

Related Party Transactions (Narrative) (Details) - Ameren Services Support Services Agreement - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Union Electric Company
Related Party Transaction [Line Items]
Due from Related Parties	$ 80	$ 77
Ameren Illinois Company
Related Party Transaction [Line Items]
Due from Related Parties	$ 83	$ 80

- Definition

For an unclassified balance sheet, amounts due from related parties including affiliates, employees, joint ventures, officers and stockholders, immediate families thereof, and pension funds.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(1))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10(3))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(C))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(B))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.3)
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

Related Party Transactions (Schedule of Affiliate Receivables and Payables) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Union Electric Company
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	$ 43	$ 46
Accounts Receivable, Related Parties, Current	23	44
Union Electric Company \| Income taxes payable to parent
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	0	0
Union Electric Company \| Income taxes receivable from parent
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	12	27
Ameren Illinois Company
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	117	64
Accounts Receivable, Related Parties, Current	9	24
Ameren Illinois Company \| Income taxes payable to parent
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	72	8
Ameren Illinois Company \| Income taxes receivable from parent
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	$ 0	$ 18

Related Party Transactions (Effects of Related-party Transactions on the Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Union Electric Company \| Ameren Missouri Power Supply Agreements with Ameren Illinois
Related Party Transaction [Line Items]
Operating Revenues	$ 2	$ 5	$ 7	$ 10
Union Electric Company \| Ameren Missouri and Ameren Illinois Rent and Facility Services
Related Party Transaction [Line Items]
Operating Revenues	6	6	18	20
Operating Expenses	1	1	1	1
Union Electric Company \| Ameren Missouri and Ameren Illinois Miscellaneous Support Services
Related Party Transaction [Line Items]
Operating Revenues	1	1	1	1
Union Electric Company \| Total Related Party Operating Revenues
Related Party Transaction [Line Items]
Operating Revenues	8	11	25	30
Union Electric Company \| Ameren Missouri and Ameren Illinois Transmission Services from ATXI
Related Party Transaction [Line Items]
Operating Expenses	1	1	1	3
Union Electric Company \| Purchased Power
Related Party Transaction [Line Items]
Operating Expenses	1	1	1	3
Union Electric Company \| Ameren Services Support Services Agreement
Related Party Transaction [Line Items]
Operating Expenses	38	41	109	110
Union Electric Company \| Total Related Party Other Operations and Maintenance
Related Party Transaction [Line Items]
Operating Expenses	38	41	109	110
Union Electric Company \| Money pool borrowings (advances)
Related Party Transaction [Line Items]
Interest Charges (Income)	1	1	1	1
Ameren Illinois Company \| Ameren Missouri and Ameren Illinois Rent and Facility Services
Related Party Transaction [Line Items]
Operating Revenues	1	1	1	1
Operating Expenses	1	1	2	3
Ameren Illinois Company \| Ameren Missouri and Ameren Illinois Miscellaneous Support Services
Related Party Transaction [Line Items]
Operating Revenues	1	3	1	5
Ameren Illinois Company \| Total Related Party Operating Revenues
Related Party Transaction [Line Items]
Operating Revenues	1	3	1	5
Ameren Illinois Company \| Ameren Illinois Power Supply Agreements with Ameren Missouri
Related Party Transaction [Line Items]
Operating Expenses	2	5	7	10
Ameren Illinois Company \| Ameren Missouri and Ameren Illinois Transmission Services from ATXI
Related Party Transaction [Line Items]
Operating Expenses	1	1	1	1
Ameren Illinois Company \| Purchased Power
Related Party Transaction [Line Items]
Operating Expenses	2	5	7	11
Ameren Illinois Company \| Ameren Services Support Services Agreement
Related Party Transaction [Line Items]
Operating Expenses	36	37	103	101
Ameren Illinois Company \| Total Related Party Other Operations and Maintenance
Related Party Transaction [Line Items]
Operating Expenses	37	38	105	104
Ameren Illinois Company \| Money pool borrowings (advances)
Related Party Transaction [Line Items]
Interest Charges (Income)	$ 1	$ 1	$ 1	$ 1

Commitments And Contingencies (Environmental Matters) (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($) energyCenter scrubber site	Dec. 31, 2021 USD ($)
Loss Contingencies [Line Items]
Asset Retirement Obligation	$ 778	$ 764
Minimum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	125
Maximum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	$ 175
Union Electric Company
Loss Contingencies [Line Items]
Number of Energy Center Scrubbers \| scrubber	2
Number of Energy Centers Constructing Wastewater Treatment Facilities \| energyCenter	3
Number of energy centers \| energyCenter	4
Number of Days to Comply after Final EPA Determination	135 days
Asset Retirement Obligation	$ 774	760
Number of Ameren Missouri Natural Gas Energy Centers Subject To IETL \| energyCenter	4
Union Electric Company \| Coal Fired Electric Generation Equipment
Loss Contingencies [Line Items]
Plant To Be Abandoned, Net	$ 600
Union Electric Company \| Minimum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	125
Union Electric Company \| Maximum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	175
Ameren Illinois Company
Loss Contingencies [Line Items]
Asset Retirement Obligation	4	$ 4
Coal Combustion Residuals Estimate \| Union Electric Company \| Minimum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	60
Coal Combustion Residuals Estimate \| Union Electric Company \| Maximum
Loss Contingencies [Line Items]
Estimated capital costs to comply with existing and known federal and state air emissions regulations	80
Manufactured Gas Plant
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 71
Manufactured Gas Plant \| Ameren Illinois Company
Loss Contingencies [Line Items]
Number of remediation sites \| site	44
Accrual for environmental loss contingencies	$ 71
Manufactured Gas Plant \| Ameren Illinois Company \| Minimum
Loss Contingencies [Line Items]
Estimate of possible loss	71
Manufactured Gas Plant \| Ameren Illinois Company \| Maximum
Loss Contingencies [Line Items]
Estimate of possible loss	145
Rush Island Energy Center \| Union Electric Company
Loss Contingencies [Line Items]
Rate Base	500
New CCR Rules Estimate
Loss Contingencies [Line Items]
Asset Retirement Obligation	49
New CCR Rules Estimate \| Union Electric Company
Loss Contingencies [Line Items]
Asset Retirement Obligation	$ 49

Callaway Energy Center (Insurance Disclosure) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($) yr
Nuclear Waste Matters [Line Items]
Decommissioning Cost	$ 7.0
Frequency of Decommissioning Cost Study	3 years
Proceeds from Insurance Settlement, Investing Activities	$ 22.0
Number Of Years The Limit Of Liability And The Maximum Potential Annual Payments Are Adjusted	5 years
Number Of Weeks Of Coverage After The First Twelve Weeks Of An Outage \| yr	1
Number Of Additional Weeks After Initial Indemnity Coverage For Power Outage \| yr	1.365
Public Liability And Nuclear Worker Liability - American Nuclear Insurers
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	$ 450.0
Insurance Maximum Coverage per Incident	0.0
Public Liability And Nuclear Worker Liability - Pool Participation
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	13,210.0
Insurance Maximum Coverage per Incident	138.0
Threshold Amount For Retrospective Insurance Assessment For Covered Loss Under Public Liability And Nuclear Worker Liability Insurance Policy	450.0
Maximum Annual Payment Per Incident At Licensed Commercial Nuclear Reactor	21.0
Public Liability
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	13,660.0
Insurance Maximum Coverage per Incident	138.0
Property Damage - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	3,200.0
Insurance Maximum Coverage per Incident	26.0
Accidental Outage - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	490.0
Insurance Maximum Coverage per Incident	7.0
Amount Of Weekly Indemnity Coverage Commencing Twelve Weeks After Power Outage	4.5
Amount Of Additional Weekly Indemnity Coverage Commencing After Initial Indemnity Coverage	3.6
Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit	490.0
Sub-Limit Of Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit For Non-Nuclear Events	328.0
Radiation Event
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	2,700.0
Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period	3,200.0
Non-Radiation Event
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	2,300.0
Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period	1,800.0
Property Damage European Mutual Association for Nuclear Insurance
Nuclear Waste Matters [Line Items]
Insurance Aggregate Maximum Coverage	$ 490.0

Retirement Benefits (Components Of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total non-service cost components	$ (45)	$ (34)	$ (138)	$ (102)
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	31	33	95	100
Interest cost	42	38	123	114
Expected return on plan assets	(80)	(74)	(240)	(223)
Prior service benefit	0	0	0	0
Actuarial loss (gain)	7	18	19	55
Total non-service cost components	(31)	(18)	(98)	(54)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	0	15	(3)	46
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	5	5	15	17
Interest cost	8	9	25	25
Expected return on plan assets	(21)	(20)	(64)	(60)
Prior service benefit	(1)	(1)	(3)	(3)
Actuarial loss (gain)	(5)	(1)	(14)	(4)
Total non-service cost components	(19)	(13)	(56)	(42)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Total	$ (14)	$ (8)	$ (41)	$ (25)

Retirement Benefits (Summary of Benefit Plan Costs Incurred) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	$ 0	$ 15	$ (3)	$ 46
Pension Plan \| Union Electric Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	0	7	(2)	22
Pension Plan \| Ameren Illinois Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	1	8	2	25
Pension Plan \| Other Affiliated Entities And Intercompany Eliminations
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(1)	0	(3)	(1)
Other Postretirement Benefit Plan, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(14)	(8)	(41)	(25)
Other Postretirement Benefit Plan, Defined Benefit \| Union Electric Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(3)	(1)	(10)	(3)
Other Postretirement Benefit Plan, Defined Benefit \| Ameren Illinois Company
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	(11)	(8)	(31)	(23)
Other Postretirement Benefit Plan, Defined Benefit \| Other Affiliated Entities And Intercompany Eliminations
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	$ 0	$ 1	$ 0	$ 1

Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Aug. 16, 2022
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21.00%	21.00%	21.00%	21.00%
Increases (decreases) from:
Amortization of deferred investment tax credit	0.00%	(1.00%)	0.00%	0.00%
Amortization of excess deferred taxes	(8.00%)	(8.00%)	(8.00%)	(9.00%)
Depreciation differences	0.00%	0.00%
Renewable and other tax credits	(4.00%)	(2.00%)	(4.00%)	(3.00%)
State tax	4.00%	4.00%	5.00%	5.00%
Stock-based compensation	1.00%	0.00%	0.00%	(1.00%)
Cash surrender value of COLI	1.00%	0.00%
Effective income tax rate	15.00%	14.00%	14.00%	13.00%
Production and Investment Tax Credit Adder					10.00%
Greenhouse Emissions Reduction Target, Inflation Reduction Act					75.00%
Tax Credit Transferability, Inflation Reduction Act, Percent					100.00%
Minimum Tax on Book Income, Percent					15.00%
Minimum Adjusted Financial Statement Income Subject to Inflation Reduction Act Tax					$ 1,000
Union Electric Company
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21.00%	21.00%	21.00%	21.00%
Increases (decreases) from:
Amortization of deferred investment tax credit	(1.00%)	(1.00%)	(1.00%)	0.00%
Amortization of excess deferred taxes	(15.00%)	(17.00%)	(15.00%)	(17.00%)
Depreciation differences	0.00%	0.00%
Renewable and other tax credits	(10.00%)	(8.00%)	(10.00%)	(8.00%)
State tax	3.00%	4.00%	3.00%	3.00%
Stock-based compensation	0.00%	0.00%	0.00%	0.00%
Cash surrender value of COLI	0.00%	0.00%
Effective income tax rate	(2.00%)	(1.00%)	(2.00%)	(1.00%)
Ameren Illinois Company
Income Taxes [Line Items]
Federal statutory corporate income tax rate	21.00%	21.00%	21.00%	21.00%
Increases (decreases) from:
Amortization of deferred investment tax credit	0.00%	0.00%	0.00%	0.00%
Amortization of excess deferred taxes	(2.00%)	(2.00%)	(2.00%)	(3.00%)
Depreciation differences	0.00%	(1.00%)
Renewable and other tax credits	0.00%	0.00%	0.00%	0.00%
State tax	7.00%	7.00%	7.00%	7.00%
Stock-based compensation	0.00%	0.00%	0.00%	0.00%
Cash surrender value of COLI	0.00%	0.00%
Effective income tax rate	26.00%	25.00%	26.00%	25.00%

Supplemental Information (Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	$ 7	$ 8
Restricted cash included in “Other current assets”	7	16
Restricted cash included in “Other assets”	162	127
Restricted cash included in “Nuclear decommissioning trust fund”	4	4
Total cash, cash equivalents, and restricted cash	180	155	$ 145	$ 301
Union Electric Company
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	0	0
Restricted cash included in “Other current assets”	3	4
Restricted cash included in “Other assets”	0	0
Restricted cash included in “Nuclear decommissioning trust fund”	4	4
Total cash, cash equivalents, and restricted cash	7	8	11	145
Ameren Illinois Company
Schedule of Cash and Cash Equivalents Including Restricted Cash [Line Items]
Cash and cash equivalents	0	0
Restricted cash included in “Other current assets”	4	6
Restricted cash included in “Other assets”	162	127
Restricted cash included in “Nuclear decommissioning trust fund”	0	0
Total cash, cash equivalents, and restricted cash	$ 166	$ 133	$ 122	$ 147

Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	$ 30	$ 42	$ 29	$ 50
Bad debt expense	15	7	26	8
Net write-offs	(14)	(13)	(24)	(22)
End of period	31	$ 36	31	$ 36
Payables for purchased receivables	$ 32		$ 32		$ 27
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	17.00%	18.00%	17.00%	18.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 117	$ 97	$ 117	$ 97
Union Electric Company
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	12	16	13	16
Bad debt expense	3	2	6	5
Net write-offs	(3)	(4)	(7)	(7)
End of period	$ 12	$ 14	$ 12	$ 14
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	12.00%	12.00%	12.00%	12.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 39	$ 33	$ 39	$ 33
Ameren Illinois Company
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	18	26	16	34
Bad debt expense	12	5	20	3
Net write-offs	(11)	(9)	(17)	(15)
End of period	19	$ 22	19	$ 22
Payables for purchased receivables	$ 32		$ 32		$ 27
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	21.00%	25.00%	21.00%	25.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 78	$ 64	$ 78	$ 64

Supplemental Information (Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Supplemental Cash Flow Information [Line Items]
Wind generation expenditures	$ 98		$ 515
Accrued capital expenditures		$ 367	396
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund		(262)	85
Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued		31	33
Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued		8	0
Union Electric Company
Supplemental Cash Flow Information [Line Items]
Wind generation expenditures	$ 98		515
Accrued capital expenditures		187	209
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund		(262)	85
Union Electric Company \| Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued		0	0
Union Electric Company \| Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued		0	0
Ameren Illinois Company
Supplemental Cash Flow Information [Line Items]
Accrued capital expenditures		180	182
Net realized and unrealized gain/(loss) – nuclear decommissioning trust fund		0	0
Ameren Illinois Company \| Issuance of common stock for stock-based compensation
Supplemental Cash Flow Information [Line Items]
Stock Issued		0	0
Ameren Illinois Company \| Issuance of common stock under the DRPlus
Supplemental Cash Flow Information [Line Items]
Stock Issued		$ 0	$ 0

Supplemental Information (Schedule of Asset Retirement Obligations) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	$ 764
Liabilities incurred	1
Liabilities settled	(3)
Accretion	23
Change in estimates	(7)
Asset Retirement Obligation, Ending Balance	778
Other current liabilities	584	$ 494
Union Electric Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	760
Liabilities incurred	1
Liabilities settled	(3)
Accretion	23
Change in estimates	(7)
Asset Retirement Obligation, Ending Balance	774
Other current liabilities	114	116
Ameren Illinois Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Beginning Balance	4
Liabilities incurred	0
Liabilities settled	0
Accretion	0
Change in estimates	0
Asset Retirement Obligation, Ending Balance	4
Other current liabilities	275	251
Asset Retirement Obligation Balance
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Other current liabilities	7	7
Asset Retirement Obligation Balance \| Union Electric Company
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Other current liabilities	$ 7	$ 7

Supplemental Information (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Available for Grant	8,800,000
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount	$ 5	$ 5
Deferred Compensation Liability, Classified, Noncurrent	$ 88		$ 91
Q1 2022 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Performance Shares \| Q1 2022 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	267,849
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value	$ 25
Stock Issued During Period Percentage Conversion Of Units, Low End	0.00%
Stock Issued During Period Percentage Conversion Of Units, High End	200.00%
Performance Shares \| Market performance measures achievement \| Q1 2022 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	229,566
Performance Shares \| Renewable generation and energy storage installation targets \| Q1 2022 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	38,283
Restricted Stock Units (RSUs) \| Q1 2022 Issuance
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	122,882
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Granted in Period, Fair Value	$ 11

Supplemental Information (Schedule Of Excise Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accounting Policies [Line Items]
Excise tax expense	$ 83	$ 81	$ 229	$ 213
Union Electric Company
Accounting Policies [Line Items]
Excise tax expense	55	54	128	120
Ameren Illinois Company
Accounting Policies [Line Items]
Excise tax expense	$ 28	$ 27	$ 101	$ 93

Supplemental Information (Earnings Per Share) (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share Reconciliation [Abstract]
Weighted-average Common Shares Outstanding – Basic	258,400,000	257,300,000	258,200,000	255,900,000
Assumed settlement of performance share units and restricted stock units	900,000	1,300,000	1,000,000.0	1,300,000
Dilutive effect of forward sale agreements	200,000	0	100,000	0
Weighted-average Common Shares Outstanding – Diluted	259,500,000	258,600,000	259,300,000	257,200,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	0	0	0	0

Segment Information (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Revenues	$ 2,306	$ 1,811	$ 5,911	$ 4,849
Net income (loss) attributable to common shareholders	452	425	911	865
Capital expenditures	899	850	2,437	2,613
Wind generation expenditures		98		515
Union Electric Company
Segment Reporting Information [Line Items]
Revenues	1,359	1,129	3,096	2,642
Net income (loss) attributable to common shareholders	397	375	547	533
Wind generation expenditures		98		515
Ameren Illinois Company
Segment Reporting Information [Line Items]
Revenues	904	645	2,697	2,097
Net income (loss) attributable to common shareholders	103	79	375	314
Capital expenditures	446	380	1,145	1,026
Operating Segments \| Union Electric Company
Segment Reporting Information [Line Items]
Revenues	1,351	1,118	3,071	2,612
Net income (loss) attributable to common shareholders	397	375	547	533
Capital expenditures	431	466	1,237	1,567
Operating Segments \| Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Revenues	672	425	1,640	1,222
Net income (loss) attributable to common shareholders	51	36	151	123
Capital expenditures	163	143	444	429
Operating Segments \| Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Revenues	146	127	811	642
Net income (loss) attributable to common shareholders	(4)	(8)	82	75
Capital expenditures	114	93	232	202
Operating Segments \| Ameren Transmission
Segment Reporting Information [Line Items]
Revenues	137	141	389	373
Net income (loss) attributable to common shareholders	78	73	199	175
Capital expenditures	187	154	519	426
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Revenues	672	428	1,641	1,227
Net income (loss) attributable to common shareholders	51	36	151	123
Capital expenditures	163	143	444	429
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Revenues	146	127	811	642
Net income (loss) attributable to common shareholders	(4)	(8)	82	75
Capital expenditures	114	93	232	202
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Transmission
Segment Reporting Information [Line Items]
Revenues	86	90	245	228
Net income (loss) attributable to common shareholders	56	51	142	116
Capital expenditures	169	144	469	395
Other
Segment Reporting Information [Line Items]
Net income (loss) attributable to common shareholders	(70)	(51)	(68)	(41)
Capital expenditures	1	2	4	3
Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment revenues	(40)	(33)	(102)	(88)
Capital expenditures	3	(8)	1	(14)
Intersegment Eliminations \| Union Electric Company
Segment Reporting Information [Line Items]
Intersegment revenues	(8)	(11)	(25)	(30)
Intersegment Eliminations \| Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Intersegment revenues	0	(3)	(1)	(5)
Intersegment Eliminations \| Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Intersegment revenues	0	0	0	0
Intersegment Eliminations \| Ameren Transmission
Segment Reporting Information [Line Items]
Intersegment revenues	(32)	(19)	(76)	(53)
Intersegment Eliminations \| Ameren Illinois Company
Segment Reporting Information [Line Items]
Intersegment revenues	(31)	(18)	(75)	(49)
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Electric Distribution
Segment Reporting Information [Line Items]
Intersegment revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Natural Gas
Segment Reporting Information [Line Items]
Intersegment revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Transmission
Segment Reporting Information [Line Items]
Intersegment revenues	$ (31)	$ (18)	$ (75)	$ (49)

Segment Information (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 2,306	$ 1,811	$ 5,911	$ 4,849
Revenues	2,306	1,811	5,911	4,849
Revenues from alternative revenue programs	(83)	(95)	2	(6)
Other revenues not from contracts with customers	(43)	13	(74)	82
Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	14	6	8	(9)
Other revenues not from contracts with customers	(45)	7	(81)	71
Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	(83)	(97)	13	(2)
Other revenues not from contracts with customers	2	6	5	9
Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	(3)	(5)	(5)	0
Other revenues not from contracts with customers	0	0	2	2
Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	(11)	1	(14)	5
Other revenues not from contracts with customers	0	0	0	0
Electric
Disaggregation of Revenue [Line Items]
Revenues	2,140	1,668	4,971	4,108
Revenues	2,140	1,668	4,971	4,108
Electric \| Residential
Disaggregation of Revenue [Line Items]
Revenues	971	795	2,221	1,882
Electric \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	663	555	1,539	1,301
Electric \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	146	124	374	315
Electric \| Other
Disaggregation of Revenue [Line Items]
Revenues	360	194	837	610
Natural gas
Disaggregation of Revenue [Line Items]
Revenues	166	143	940	741
Revenues	166	143	940	741
Natural gas \| Residential
Disaggregation of Revenue [Line Items]
Revenues	100	84	653	492
Natural gas \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	31	27	188	139
Natural gas \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	6	3	37	22
Natural gas \| Other
Disaggregation of Revenue [Line Items]
Revenues	29	29	62	88
Ameren Illinois Company
Disaggregation of Revenue [Line Items]
Revenues	904	645	2,697	2,097
Revenues	904	645	2,697	2,097
Revenues from alternative revenue programs	(96)	(99)	(4)	2
Other revenues not from contracts with customers	2	6	7	11
Ameren Illinois Company \| Residential
Disaggregation of Revenue [Line Items]
Revenues	496	333	1,529	1,143
Ameren Illinois Company \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	258	166	723	518
Ameren Illinois Company \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	52	29	178	114
Ameren Illinois Company \| Other
Disaggregation of Revenue [Line Items]
Revenues	98	117	267	322
Ameren Illinois Company \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	(83)	(97)	13	(2)
Other revenues not from contracts with customers	2	6	5	9
Ameren Illinois Company \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	(3)	(5)	(5)	0
Other revenues not from contracts with customers	0	0	2	2
Ameren Illinois Company \| Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues from alternative revenue programs	(10)	3	(12)	4
Other revenues not from contracts with customers	0	0	0	0
Ameren Illinois Company \| Electric
Disaggregation of Revenue [Line Items]
Revenues	758	518	1,886	1,455
Ameren Illinois Company \| Natural gas
Disaggregation of Revenue [Line Items]
Revenues	146	127	811	642
Operating Segments \| Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	1,351	1,118	3,071	2,612
Revenues	1,359	1,129	3,096	2,642
Operating Segments \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	672	425	1,640	1,222
Revenues	672	428	1,641	1,227
Operating Segments \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	146	127	811	642
Revenues	146	127	811	642
Operating Segments \| Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	137	141	389	373
Revenues	169	160	465	426
Operating Segments \| Electric \| Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	1,338	1,113	2,966	2,543
Operating Segments \| Electric \| Union Electric Company \| Residential
Disaggregation of Revenue [Line Items]
Revenues	564	537	1,267	1,177
Operating Segments \| Electric \| Union Electric Company \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	430	412	968	899
Operating Segments \| Electric \| Union Electric Company \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	99	98	229	221
Operating Segments \| Electric \| Union Electric Company \| Other
Disaggregation of Revenue [Line Items]
Revenues	245	66	502	246
Operating Segments \| Electric \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	672	428	1,641	1,227
Operating Segments \| Electric \| Ameren Illinois Electric Distribution \| Residential
Disaggregation of Revenue [Line Items]
Revenues	407	258	954	705
Operating Segments \| Electric \| Ameren Illinois Electric Distribution \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	233	143	571	402
Operating Segments \| Electric \| Ameren Illinois Electric Distribution \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	47	26	145	94
Operating Segments \| Electric \| Ameren Illinois Electric Distribution \| Other
Disaggregation of Revenue [Line Items]
Revenues	(15)	1	(29)	26
Operating Segments \| Electric \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Illinois Natural Gas \| Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Illinois Natural Gas \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Illinois Natural Gas \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Illinois Natural Gas \| Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	169	160	465	426
Operating Segments \| Electric \| Ameren Transmission \| Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Transmission \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Transmission \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Electric \| Ameren Transmission \| Other
Disaggregation of Revenue [Line Items]
Revenues	169	160	465	426
Operating Segments \| Natural gas \| Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	21	16	130	99
Operating Segments \| Natural gas \| Union Electric Company \| Residential
Disaggregation of Revenue [Line Items]
Revenues	11	9	78	54
Operating Segments \| Natural gas \| Union Electric Company \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	6	4	36	23
Operating Segments \| Natural gas \| Union Electric Company \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	1	0	4	2
Operating Segments \| Natural gas \| Union Electric Company \| Other
Disaggregation of Revenue [Line Items]
Revenues	3	3	12	20
Operating Segments \| Natural gas \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Illinois Electric Distribution \| Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Illinois Electric Distribution \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Illinois Electric Distribution \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Illinois Electric Distribution \| Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	146	127	811	642
Operating Segments \| Natural gas \| Ameren Illinois Natural Gas \| Residential
Disaggregation of Revenue [Line Items]
Revenues	89	75	575	438
Operating Segments \| Natural gas \| Ameren Illinois Natural Gas \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	25	23	152	116
Operating Segments \| Natural gas \| Ameren Illinois Natural Gas \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	5	3	33	20
Operating Segments \| Natural gas \| Ameren Illinois Natural Gas \| Other
Disaggregation of Revenue [Line Items]
Revenues	27	26	51	68
Operating Segments \| Natural gas \| Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Transmission \| Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Transmission \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Transmission \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Natural gas \| Ameren Transmission \| Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	672	428	1,641	1,227
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	146	127	811	642
Operating Segments \| Ameren Illinois Company \| Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	86	90	245	228
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	672	428	1,641	1,227
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Electric Distribution \| Residential
Disaggregation of Revenue [Line Items]
Revenues	407	258	954	705
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Electric Distribution \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	233	143	571	402
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Electric Distribution \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	47	26	145	94
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Electric Distribution \| Other
Disaggregation of Revenue [Line Items]
Revenues	(15)	1	(29)	26
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	117	108	320	277
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Transmission \| Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Transmission \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Transmission \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Operating Segments \| Ameren Illinois Company \| Electric \| Ameren Illinois Transmission \| Other
Disaggregation of Revenue [Line Items]
Revenues	117	108	320	277
Operating Segments \| Ameren Illinois Company \| Natural gas \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	146	127	811	642
Operating Segments \| Ameren Illinois Company \| Natural gas \| Ameren Illinois Natural Gas \| Residential
Disaggregation of Revenue [Line Items]
Revenues	89	75	575	438
Operating Segments \| Ameren Illinois Company \| Natural gas \| Ameren Illinois Natural Gas \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	25	23	152	116
Operating Segments \| Ameren Illinois Company \| Natural gas \| Ameren Illinois Natural Gas \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	5	3	33	20
Operating Segments \| Ameren Illinois Company \| Natural gas \| Ameren Illinois Natural Gas \| Other
Disaggregation of Revenue [Line Items]
Revenues	27	26	51	68
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenues	(40)	(33)	(102)	(88)
Revenues	(40)	(33)	(102)	(88)
Intersegment Eliminations \| Union Electric Company
Disaggregation of Revenue [Line Items]
Revenues	(8)	(11)	(25)	(30)
Intersegment Eliminations \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	(3)	(1)	(5)
Intersegment Eliminations \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Transmission
Disaggregation of Revenue [Line Items]
Revenues	(32)	(19)	(76)	(53)
Intersegment Eliminations \| Electric
Disaggregation of Revenue [Line Items]
Revenues	(39)	(33)	(101)	(88)
Intersegment Eliminations \| Electric \| Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Electric \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Electric \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Electric \| Other
Disaggregation of Revenue [Line Items]
Revenues	(39)	(33)	(101)	(88)
Intersegment Eliminations \| Natural gas
Disaggregation of Revenue [Line Items]
Revenues	(1)	0	(1)	0
Intersegment Eliminations \| Natural gas \| Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Natural gas \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Natural gas \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Natural gas \| Other
Disaggregation of Revenue [Line Items]
Revenues	(1)	0	(1)	0
Intersegment Eliminations \| Ameren Illinois Company
Disaggregation of Revenue [Line Items]
Revenues	(31)	(18)	(75)	(49)
Revenues	(31)	(18)	(75)	(49)
Intersegment Eliminations \| Ameren Illinois Company \| Residential
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Commercial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Industrial
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Other
Disaggregation of Revenue [Line Items]
Revenues	(31)	(18)	(75)	(49)
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Electric Distribution
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Natural Gas
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Intersegment Eliminations \| Ameren Illinois Company \| Ameren Illinois Transmission
Disaggregation of Revenue [Line Items]
Revenues	$ (31)	$ (18)	$ (75)	$ (49)