Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2020	Oct. 08, 2020
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Commission File Number	1-9513
Entity Registrant Name	CMS ENERGY CORPORATION
IRS Employer Identification No.	38-2726431
Entity Incorporation State	MI
Entity Address	One Energy Plaza
City	Jackson
State	MI
Postal Zip Code	49201
City Area Code	517
Local Phone Number	788‑0550
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Smaller reporting company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		286,334,466
Entity Central Index Key	0000811156
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Consumers Energy Company
Document Information [Line Items]
Commission File Number	1-5611
Entity Registrant Name	CONSUMERS ENERGY COMPANY
IRS Employer Identification No.	38-0442310
Entity Incorporation State	MI
Entity Address	One Energy Plaza
City	Jackson
State	MI
Postal Zip Code	49201
City Area Code	517
Local Phone Number	788‑0550
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Smaller reporting company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		84,108,789
Entity Central Index Key	0000201533
Common Stock
Document Information [Line Items]
Title of each class	CMS Energy Corporation Common Stock, $0.01 par value
Trading Symbol	CMS
Security Exchange Name	NYSE
CMS Energy Corporation 5.625% Junior Subordinated Notes due 2078
Document Information [Line Items]
Title of each class	CMS Energy Corporation 5.625% Junior Subordinated Notes due 2078
Trading Symbol	CMSA
Security Exchange Name	NYSE
CMS Energy Corporation 5.875% Junior Subordinated Notes due 2078
Document Information [Line Items]
Title of each class	CMS Energy Corporation 5.875% Junior Subordinated Notes due 2078
Trading Symbol	CMSC
Security Exchange Name	NYSE
CMS Energy Corporation 5.875% Junior Subordinated Notes due 2079
Document Information [Line Items]
Title of each class	CMS Energy Corporation 5.875% Junior Subordinated Notes due 2079
Trading Symbol	CMSD
Security Exchange Name	NYSE
Consumers Energy Company Cumulative Preferred Stock, $100 par value: $4.50 Series
Document Information [Line Items]
Title of each class	Consumers Energy Company Cumulative Preferred Stock, $100 par value: $4.50 Series
Trading Symbol	CMS-PB
Security Exchange Name	NYSE

Consolidated Statements of Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating Revenue	$ 1,575	$ 1,546	$ 4,882	$ 5,050
Operating Expenses
Fuel for electric generation	108	130	274	391
Purchased power – related parties	13	19	45	53
Maintenance and other operating expenses	317	313	983	1,010
Depreciation and amortization	228	215	767	729
General taxes	75	70	264	247
Total operating expenses	1,206	1,195	3,872	4,122
Operating Income	369	351	1,010	928
Other Income (Expense)
Interest income	1	2	3	5
Interest and dividend income – related parties	0	0	7	0
Allowance for equity funds used during construction	1	2	4	7
Income from equity method investees	0	5	1	6
Nonoperating retirement benefits, net	29	22	90	68
Other income	1	0	3	3
Other expense	(4)	0	(9)	(8)
Total other income	28	31	99	81
Interest Charges
Interest on long-term debt	124	111	361	327
Interest expense – related parties	3	3	9	6
Other interest expense	17	20	53	55
Allowance for borrowed funds used during construction	(1)	(1)	(2)	(3)
Total interest charges	143	133	421	385
Income Before Income Taxes	254	249	688	624
Income Tax Expense	44	42	98	110
Net Income	210	207	590	514
Income (Loss) Attributable to Noncontrolling Interests	(8)	0	(7)	1
Net Income Available to Common Stockholders	$ 218	$ 207	$ 597	$ 513
Basic earnings per average common share (in dollars per share)	$ 0.76	$ 0.73	$ 2.10	$ 1.81
Diluted earnings per average common share (in dollars per share)	$ 0.76	$ 0.73	$ 2.09	$ 1.81
Consumers Energy Company
Operating Revenue	$ 1,450	$ 1,429	$ 4,524	$ 4,706
Operating Expenses
Fuel for electric generation	85	101	207	295
Purchased and interchange power	420	408	1,121	1,132
Purchased power – related parties	13	19	45	53
Cost of gas sold	33	32	383	537
Maintenance and other operating expenses	266	272	846	911
Depreciation and amortization	223	210	753	716
General taxes	72	68	256	240
Total operating expenses	1,112	1,110	3,611	3,884
Operating Income	338	319	913	822
Other Income (Expense)
Interest income	1	2	3	4
Interest and dividend income – related parties	2	1	4	3
Allowance for equity funds used during construction	1	2	4	7
Nonoperating retirement benefits, net	28	21	85	64
Other income	1	0	3	2
Other expense	(4)	0	(9)	(8)
Total other income	29	26	90	72
Interest Charges
Interest on long-term debt	76	69	227	206
Interest expense – related parties	3	3	9	6
Other interest expense	4	4	9	11
Allowance for borrowed funds used during construction	(1)	(1)	(2)	(3)
Total interest charges	82	75	243	220
Income Before Income Taxes	285	270	760	674
Income Tax Expense	55	57	135	137
Net Income	230	213	625	537
Preferred Stock Dividends	0	0	1	1
Net Income Available to Common Stockholder	230	213	624	536
Purchased and interchange power
Operating Expenses
Cost of sales	430	413	1,149	1,147
Cost of gas sold
Operating Expenses
Cost of sales	$ 35	$ 35	$ 390	$ 545

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net income	$ 210	$ 207	$ 590	$ 514
Retirement Benefits Liability
Net loss arising during the period, net of tax of $(2), $-, $(2), and $-	(5)	0	(5)	0
Settlement arising during the period, net of tax of $- for all periods	1	0	1	0
Amortization of net actuarial loss, net of tax	1	0	3	2
Amortization of prior service credit, net of tax of $- for all periods	0	0	(1)	(1)
Derivatives
Unrealized loss on derivative instruments, net of tax of $-, $-, $(1), and $(1)	(1)	0	(5)	(3)
Reclassification adjustments included in net income	1	0	1	0
Other Comprehensive Loss	(3)	0	(6)	(2)
Comprehensive Income	207	207	584	512
Comprehensive Income (Loss) Attributable to Noncontrolling Interests	(8)	0	(7)	1
Comprehensive Income Attributable to CMS Energy	215	207	591	511
Consumers Energy Company
Net income	230	213	625	537
Retirement Benefits Liability
Amortization of net actuarial loss, net of tax	1	0	1	1
Derivatives
Other Comprehensive Loss	1	0	1	1
Comprehensive Income	$ 231	$ 213	$ 626	$ 538

Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net loss arising during the period, TAX BENEFIT	$ (2)	$ 0	$ (2)	$ 0
Settlement arising during the period, TAX	0	0	0	0
Amortization of net actuarial loss, TAX	0	0	1	0
Amortization of prior service credit, TAX	0	0	0	0
Unrealized loss on derivative instruments, TAX BENEFIT	0	0	(1)	(1)
Reclassification adjustments included in net income, TAX	0	0	0	0
Consumers Energy Company
Amortization of net actuarial loss, TAX	$ 0	$ 0	$ 1	$ 0

Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash Flows from Operating Activities
Net income	$ 590	$ 514
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	767	729
Deferred income taxes and investment tax credits	140	89
Pension contributions	(531)	0
Other non-cash operating activities and reconciling adjustments	24	(11)
Cash provided by (used in) changes in assets and liabilities
Accounts and notes receivable and accrued revenue	218	297
Inventories	(34)	(49)
Accounts payable and accrued rate refunds	29	(82)
Other current and non-current assets and liabilities	(59)	(92)
Net cash provided by operating activities	1,144	1,395
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under finance lease)	(1,697)	(1,570)
Increase in EnerBank notes receivable	(480)	(328)
Purchase of notes receivable by EnerBank	(17)	(307)
Proceeds from sale of transmission equipment	0	96
Cost to retire property and other investing activities	(104)	(103)
Net cash used in investing activities	(2,298)	(2,212)
Cash Flows from Financing Activities
Proceeds from issuance of debt	2,353	2,076
Retirement of debt	(1,294)	(1,170)
Increase in EnerBank certificates of deposit	456	622
Decrease in notes payable	(90)	(97)
Issuance of common stock, net of issuance costs	107	9
Payment of dividends on common and preferred stock	(351)	(326)
Proceeds from the sale of membership interest in VIE to tax equity investor	417	0
Contribution from noncontrolling interest	31	0
Other financing costs	(74)	(39)
Net cash provided by financing activities	1,555	1,075
Net Increase in Cash and Cash Equivalents, Including Restricted Amounts	401	258
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	157	175
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	558	433
Non-cash transactions
Capital expenditures not paid	140	135
Consumers Energy Company
Cash Flows from Operating Activities
Net income	625	537
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	753	716
Deferred income taxes and investment tax credits	136	37
Pension contributions	(518)	0
Other non-cash operating activities and reconciling adjustments	(21)	(24)
Cash provided by (used in) changes in assets and liabilities
Accounts and notes receivable and accrued revenue	190	230
Inventories	(34)	(52)
Accounts payable and accrued rate refunds	29	(76)
Other current and non-current assets and liabilities	(75)	(117)
Net cash provided by operating activities	1,085	1,251
Cash Flows from Investing Activities
Capital expenditures (excludes assets placed under finance lease)	(1,595)	(1,559)
Proceeds from sale of transmission equipment	0	76
Cost to retire property and other investing activities	(105)	(100)
Net cash used in investing activities	(1,700)	(1,583)
Cash Flows from Financing Activities
Proceeds from issuance of debt	1,528	918
Retirement of debt	(773)	(528)
Decrease in notes payable	(90)	(97)
Stockholder contribution	650	675
Payment of dividends on common and preferred stock	(450)	(397)
Other financing costs	(55)	(11)
Net cash provided by financing activities	810	560
Net Increase in Cash and Cash Equivalents, Including Restricted Amounts	195	228
Cash and Cash Equivalents, Including Restricted Amounts, Beginning of Period	28	56
Cash and Cash Equivalents, Including Restricted Amounts, End of Period	223	284
Non-cash transactions
Capital expenditures not paid	$ 156	$ 123

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Current Assets
Cash and cash equivalents	$ 519	$ 140
Restricted cash and cash equivalents	39	17
Accounts receivable and accrued revenue, less allowance of $30 in 2020 and $20 in 2019	648	886
Notes receivable, less allowance of $35 in 2020 and $33 in 2019	272	242
Accounts and notes receivable – related parties	21	17
Inventories at average cost
Gas in underground storage	420	399
Materials and supplies	154	140
Generating plant fuel stock	65	66
Deferred property taxes	199	305
Regulatory assets	9	33
Prepayments and other current assets	148	86
Total current assets	2,494	2,331
Plant, Property, and Equipment
Plant, property, and equipment, gross	27,036	25,390
Less accumulated depreciation and amortization	7,845	7,360
Plant, property, and equipment, net	19,191	18,030
Construction work in progress	1,439	896
Total plant, property, and equipment	20,630	18,926
Other Non-current Assets
Regulatory assets	2,745	2,489
Accounts and notes receivable, less allowance	2,655	2,281
Investments	68	71
Other	688	739
Total other non-current assets	6,156	5,580
Total Assets	29,280	26,837
Current Liabilities
Current portion of long-term debt, finance leases, and other financing	1,799	1,130
Notes payable	0	90
Accounts payable	662	622
Accounts payable – related parties	5	13
Accrued rate refunds	28	35
Accrued interest	108	104
Accrued taxes	128	437
Regulatory liabilities	69	87
Other current liabilities	193	186
Total current liabilities	2,992	2,704
Non-current Liabilities
Long-term debt	13,275	11,951
Non-current portion of finance leases and other financing	61	76
Regulatory liabilities	3,796	3,742
Postretirement benefits	382	674
Asset retirement obligations	510	477
Deferred investment tax credit	116	120
Deferred income taxes	1,821	1,655
Other non-current liabilities	429	383
Total non-current liabilities	20,390	19,078
Commitments and contingencies
Common stockholders’ equity
Common stock	3	3
Other paid-in capital	5,225	5,113
Accumulated other comprehensive loss	(79)	(73)
Retained earnings (accumulated deficit)	171	(25)
Total common stockholders’ equity	5,320	5,018
Noncontrolling interests	578	37
Total equity	5,898	5,055
Total Liabilities and Equity	29,280	26,837
Consumers Energy Company
Current Assets
Cash and cash equivalents	199	11
Restricted cash and cash equivalents	24	17
Accounts receivable and accrued revenue, less allowance of $30 in 2020 and $20 in 2019	620	827
Accounts and notes receivable – related parties	8	9
Inventories at average cost
Gas in underground storage	420	399
Materials and supplies	149	135
Generating plant fuel stock	62	63
Deferred property taxes	199	305
Regulatory assets	9	33
Prepayments and other current assets	126	73
Total current assets	1,816	1,872
Plant, Property, and Equipment
Plant, property, and equipment, gross	25,893	24,963
Less accumulated depreciation and amortization	7,747	7,272
Plant, property, and equipment, net	18,146	17,691
Construction work in progress	1,422	879
Total plant, property, and equipment	19,568	18,570
Other Non-current Assets
Regulatory assets	2,745	2,489
Accounts and notes receivable, less allowance	26	29
Accounts and notes receivable – related parties	106	102
Other	575	637
Total other non-current assets	3,452	3,257
Total Assets	24,836	23,699
Current Liabilities
Current portion of long-term debt, finance leases, and other financing	557	221
Notes payable	0	90
Accounts payable	626	593
Accounts payable – related parties	10	20
Accrued rate refunds	28	35
Accrued interest	78	67
Accrued taxes	134	481
Regulatory liabilities	69	87
Other current liabilities	124	118
Total current liabilities	1,626	1,712
Non-current Liabilities
Long-term debt	7,458	7,048
Non-current portion of finance leases and other financing	61	76
Regulatory liabilities	3,796	3,742
Postretirement benefits	339	622
Asset retirement obligations	486	474
Deferred investment tax credit	116	120
Deferred income taxes	2,042	1,864
Other non-current liabilities	349	304
Total non-current liabilities	14,647	14,250
Commitments and contingencies
Common stockholders’ equity
Common stock	841	841
Other paid-in capital	6,024	5,374
Accumulated other comprehensive loss	(27)	(28)
Retained earnings (accumulated deficit)	1,688	1,513
Total common stockholders’ equity	8,526	7,700
Cumulative preferred stock, $4.50 series	37	37
Total equity	8,563	7,737
Total Liabilities and Equity	$ 24,836	$ 23,699

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Accounts receivable and accrued revenue ALLOWANCE	$ 30	$ 20
Notes receivable – current ALLOWANCE	35	33
Accounts and notes receivable – non-current ALLOWANCE	$ 81	$ 0
Common stock, authorized (in shares)	350,000,000.0	350,000,000.0
Common stock, outstanding (in shares)	286,300,000	283,900,000
Consumers Energy Company
Accounts receivable and accrued revenue ALLOWANCE	$ 30	$ 20
Common stock, authorized (in shares)	125,000,000	125,000,000
Common stock, outstanding (in shares)	84,100,000	84,100,000
Preferred stock, par value (in dollars per share)	$ 4.50	$ 4.50

Consolidated Statements of Changes In Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock	Other Paid-in Capital	Accumulated Other Comprehensive Loss	Retirement benefits liability	Derivative instruments	Retained Earnings (Accumulated Deficit)	Noncontrolling Interests	Consumers Energy Company	Consumers Energy Company Common Stock	Consumers Energy Company Other Paid-in Capital	Consumers Energy Company Accumulated Other Comprehensive Loss	Consumers Energy Company Retirement benefits liability	Consumers Energy Company Retained Earnings (Accumulated Deficit)	Consumers Energy Company Preferred Stock	Cumulative effect of change in accounting principle Retained Earnings (Accumulated Deficit)
Total Equity at Beginning of Period at Dec. 31, 2018	$ 4,792	$ 3	$ 5,088	$ (65)	$ (63)	$ (2)	$ (271)	$ 37	$ 6,920	$ 841	$ 4,699	$ (21)	$ (21)	$ 1,364	$ 37	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued			25
Net loss arising during the period	0				0
Settlement arising during the period	0				0
Common stock repurchased			(9)
Stockholder contribution											675
Amortization of net actuarial loss	2				2				1				1
Amortization of prior service credit	(1)				(1)
Unrealized loss on derivative instruments	(3)					(3)
Reclassification adjustments included in net income	0					0
Net income	514						513	1	537					537
Dividends declared on common stock							(325)							(396)
Dividends declared on preferred stock														(1)
Impact of purchase and consolidation of VIE								0
Sale of membership interest in VIE to tax equity investor								0
Contribution from noncontrolling interest								0
Distributions and other changes in noncontrolling interests								(1)
Total Equity at End of Period at Sep. 30, 2019	$ 4,994	3	5,104	(67)	(62)	(5)	(83)	37	7,736	841	5,374	(20)	(20)	1,504	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in dollars per share)	$ 1.1475
Total Equity at Beginning of Period at Jun. 30, 2019	$ 4,888	3	5,097	(67)	(62)	(5)	(182)	37	7,647	841	5,374	(20)	(20)	1,415	37	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued			8
Net loss arising during the period	0				0
Settlement arising during the period	0				0
Common stock repurchased			(1)
Stockholder contribution											0
Amortization of net actuarial loss	0				0				0				0
Amortization of prior service credit	0				0
Unrealized loss on derivative instruments	0					0
Reclassification adjustments included in net income	0					0
Net income	207						207	0	213					213
Dividends declared on common stock							(108)							(124)
Dividends declared on preferred stock														0
Impact of purchase and consolidation of VIE								0
Sale of membership interest in VIE to tax equity investor								0
Contribution from noncontrolling interest								0
Distributions and other changes in noncontrolling interests								0
Total Equity at End of Period at Sep. 30, 2019	$ 4,994	3	5,104	(67)	(62)	(5)	(83)	37	7,736	841	5,374	(20)	(20)	1,504	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in dollars per share)	$ 0.3825
Total Equity at Beginning of Period at Dec. 31, 2019	$ 5,055	3	5,113	(73)	(69)	(4)	(25)	37	7,737	841	5,374	(28)	(28)	1,513	37	(51)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued			125
Net loss arising during the period	(5)				(5)
Settlement arising during the period	1				1
Common stock repurchased			(13)
Stockholder contribution											650
Amortization of net actuarial loss	3				3				1				1
Amortization of prior service credit	(1)				(1)
Unrealized loss on derivative instruments	(5)					(5)
Reclassification adjustments included in net income	1					1
Net income	590						597	(7)	625					625
Dividends declared on common stock							(350)							(449)
Dividends declared on preferred stock														(1)
Impact of purchase and consolidation of VIE								101
Sale of membership interest in VIE to tax equity investor								417
Contribution from noncontrolling interest								31
Distributions and other changes in noncontrolling interests								(1)
Total Equity at End of Period at Sep. 30, 2020	$ 5,898	3	5,225	(79)	(71)	(8)	171	578	8,563	841	6,024	(27)	(27)	1,688	37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in dollars per share)	$ 1.2225
Total Equity at Beginning of Period at Jun. 30, 2020	$ 5,251	3	5,217	(76)	(68)	(8)	70	37	8,505	841	6,024	(28)	(28)	1,631	37	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued			8
Net loss arising during the period	(5)				(5)
Settlement arising during the period	1				1
Common stock repurchased			0
Stockholder contribution											0
Amortization of net actuarial loss	1				1				1				1
Amortization of prior service credit	0				0
Unrealized loss on derivative instruments	(1)					(1)
Reclassification adjustments included in net income	1					1
Net income	210						218	(8)	230					230
Dividends declared on common stock							(117)							(173)
Dividends declared on preferred stock														0
Impact of purchase and consolidation of VIE								101
Sale of membership interest in VIE to tax equity investor								417
Contribution from noncontrolling interest								31
Distributions and other changes in noncontrolling interests								0
Total Equity at End of Period at Sep. 30, 2020	$ 5,898	$ 3	$ 5,225	$ (79)	$ (71)	$ (8)	$ 171	$ 578	$ 8,563	$ 841	$ 6,024	$ (27)	$ (27)	$ 1,688	$ 37
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (in dollars per share)	$ 0.4075

New Accounting Standards	9 Months Ended
New Accounting Standards	Sep. 30, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Standards	New Accounting Standards Implementation of New Accounting Standards ASU 2016‑13, Measurement of Credit Losses on Financial Instruments: This standard, which was effective on January 1, 2020 for CMS Energy and Consumers, provides new guidance for measuring and recognizing credit losses on financial instruments. The standard applies to financial assets that are not measured at fair value through net income as well as to certain off‑balance-sheet credit exposures. CMS Energy and Consumers were required to apply the standard using a modified retrospective approach, under which the initial impacts of the standard are recorded through a cumulative‑effect adjustment to beginning retained earnings on the effective date. The standard required an increase to the allowance for loan losses at EnerBank. Prior to the standard, the allowance reflected expected credit losses over a 12‑month period, but the new guidance requires the allowance to reflect expected credit losses over the entire life of the loans. As a result, CMS Energy recorded a $65 million increase to its expected credit loss reserves on January 1, 2020, with the offsetting adjustment recorded to retained earnings, net of taxes of $14 million. The standard also requires an increase in the initial provision for loan losses recognized in net income for new loans originated in 2020 and beyond. The adoption of this standard resulted in a $15 million reduction to CMS Energy’s income before income taxes for the nine months ended September 30, 2020. For further information on EnerBank’s loans and the related allowance for loan losses, see Note 7, Notes Receivable. At Consumers, the standard applies to the allowance for uncollectible accounts, but did not result in any significant changes to the allowance methodology and did not have a material impact on Consumers’ consolidated financial statements. ASU 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting: This standard, which was effective as of March 12, 2020 for CMS Energy and Consumers, provides optional guidance intended to ease the potential burden in accounting for the expected discontinuation of LIBOR as a reference rate in the financial markets. The guidance can be applied to modifications made to certain contracts to replace LIBOR with a new reference rate. The guidance, if elected, will permit entities to treat such modifications as the continuation of the original contract, without any required accounting reassessments or remeasurements. The guidance will also facilitate the continuation of hedge accounting for derivatives that may have to be modified to incorporate a new rate. The guidance is effective through December 31, 2022. CMS Energy and Consumers presently have various contracts that reference LIBOR and they are assessing how this standard may be applied to specific contract modifications.
Consumers Energy Company
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Standards	New Accounting Standards Implementation of New Accounting Standards ASU 2016‑13, Measurement of Credit Losses on Financial Instruments: This standard, which was effective on January 1, 2020 for CMS Energy and Consumers, provides new guidance for measuring and recognizing credit losses on financial instruments. The standard applies to financial assets that are not measured at fair value through net income as well as to certain off‑balance-sheet credit exposures. CMS Energy and Consumers were required to apply the standard using a modified retrospective approach, under which the initial impacts of the standard are recorded through a cumulative‑effect adjustment to beginning retained earnings on the effective date. The standard required an increase to the allowance for loan losses at EnerBank. Prior to the standard, the allowance reflected expected credit losses over a 12‑month period, but the new guidance requires the allowance to reflect expected credit losses over the entire life of the loans. As a result, CMS Energy recorded a $65 million increase to its expected credit loss reserves on January 1, 2020, with the offsetting adjustment recorded to retained earnings, net of taxes of $14 million. The standard also requires an increase in the initial provision for loan losses recognized in net income for new loans originated in 2020 and beyond. The adoption of this standard resulted in a $15 million reduction to CMS Energy’s income before income taxes for the nine months ended September 30, 2020. For further information on EnerBank’s loans and the related allowance for loan losses, see Note 7, Notes Receivable. At Consumers, the standard applies to the allowance for uncollectible accounts, but did not result in any significant changes to the allowance methodology and did not have a material impact on Consumers’ consolidated financial statements. ASU 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting: This standard, which was effective as of March 12, 2020 for CMS Energy and Consumers, provides optional guidance intended to ease the potential burden in accounting for the expected discontinuation of LIBOR as a reference rate in the financial markets. The guidance can be applied to modifications made to certain contracts to replace LIBOR with a new reference rate. The guidance, if elected, will permit entities to treat such modifications as the continuation of the original contract, without any required accounting reassessments or remeasurements. The guidance will also facilitate the continuation of hedge accounting for derivatives that may have to be modified to incorporate a new rate. The guidance is effective through December 31, 2022. CMS Energy and Consumers presently have various contracts that reference LIBOR and they are assessing how this standard may be applied to specific contract modifications.

Regulatory Matters	9 Months Ended
Regulatory Matters	Sep. 30, 2020
Public Utilities, General Disclosures [Line Items]
Regulatory Matters	Regulatory Matters Regulatory matters are critical to Consumers. The Michigan Attorney General, ABATE, the MPSC Staff, and certain other parties typically participate in MPSC proceedings concerning Consumers, such as Consumers’ rate cases and PSCR and GCR processes. These parties often challenge various aspects of those proceedings, including the prudence of Consumers’ policies and practices, and seek cost disallowances and other relief. The parties also have appealed significant MPSC orders. Depending upon the specific issues, the outcomes of rate cases and proceedings, including judicial proceedings challenging MPSC orders or other actions, could negatively affect CMS Energy’s and Consumers’ liquidity, financial condition, and results of operations. Consumers cannot predict the outcome of these proceedings. There are multiple appeals pending that involve various issues concerning cost recovery from customers, the adequacy of the record of evidence supporting the recovery of Smart Energy investments, and other matters. Consumers is unable to predict the outcome of these appeals. COVID‑19 Costs Accounting Deferral: In April 2020, the MPSC issued an order authorizing Consumers to defer uncollectible accounts expense incurred beginning March 24, 2020 that are in excess of the amount used to set existing rates. At September 30, 2020, Consumers had recorded $5 million of incremental uncollectible accounts expense as a non‑current regulatory asset. Voluntary Transmission Asset Sale Gain Share: In September 2019, Consumers completed a sale of a portion of its electric utility’s substation transmission equipment to METC. In December 2019, Consumers filed an application with the MPSC requesting approval to share voluntarily half of the gain from the sale with customers; this application was approved by the MPSC in April 2020. As a result, Consumers deferred $17 million of the gain as a regulatory liability in December 2019 and shared that gain with customers in 2020. Energy Waste Reduction Plan Incentive: Consumers filed its 2019 waste reduction reconciliation in June 2020, requesting the MPSC’s approval to collect from customers the maximum performance incentive of $34 million for exceeding its statutory savings targets in 2019. Consumers recognized incentive revenue under this program of $34 million in 2019.
Consumers Energy Company
Public Utilities, General Disclosures [Line Items]
Regulatory Matters	Regulatory Matters Regulatory matters are critical to Consumers. The Michigan Attorney General, ABATE, the MPSC Staff, and certain other parties typically participate in MPSC proceedings concerning Consumers, such as Consumers’ rate cases and PSCR and GCR processes. These parties often challenge various aspects of those proceedings, including the prudence of Consumers’ policies and practices, and seek cost disallowances and other relief. The parties also have appealed significant MPSC orders. Depending upon the specific issues, the outcomes of rate cases and proceedings, including judicial proceedings challenging MPSC orders or other actions, could negatively affect CMS Energy’s and Consumers’ liquidity, financial condition, and results of operations. Consumers cannot predict the outcome of these proceedings. There are multiple appeals pending that involve various issues concerning cost recovery from customers, the adequacy of the record of evidence supporting the recovery of Smart Energy investments, and other matters. Consumers is unable to predict the outcome of these appeals. COVID‑19 Costs Accounting Deferral: In April 2020, the MPSC issued an order authorizing Consumers to defer uncollectible accounts expense incurred beginning March 24, 2020 that are in excess of the amount used to set existing rates. At September 30, 2020, Consumers had recorded $5 million of incremental uncollectible accounts expense as a non‑current regulatory asset. Voluntary Transmission Asset Sale Gain Share: In September 2019, Consumers completed a sale of a portion of its electric utility’s substation transmission equipment to METC. In December 2019, Consumers filed an application with the MPSC requesting approval to share voluntarily half of the gain from the sale with customers; this application was approved by the MPSC in April 2020. As a result, Consumers deferred $17 million of the gain as a regulatory liability in December 2019 and shared that gain with customers in 2020. Energy Waste Reduction Plan Incentive: Consumers filed its 2019 waste reduction reconciliation in June 2020, requesting the MPSC’s approval to collect from customers the maximum performance incentive of $34 million for exceeding its statutory savings targets in 2019. Consumers recognized incentive revenue under this program of $34 million in 2019.

Contingencies and Commitments

9 Months Ended

Sep. 30, 2020

Site Contingency [Line Items]

Contingencies and Commitments

CMS Energy and Consumers are involved in various matters that give rise to contingent liabilities. Depending on the specific issues, the resolution of these contingencies could negatively affect CMS Energy’s and Consumers’ liquidity, financial condition, and results of operations. In their disclosures of these matters, CMS Energy and Consumers provide an estimate of the possible loss or range of loss when such an estimate can be made. Disclosures that state that CMS Energy or Consumers cannot predict the outcome of a matter indicate that they are unable to estimate a possible loss or range of loss for the matter.

CMS Energy Contingencies

Gas Index Price Reporting Litigation: CMS Energy, along with CMS MST, CMS Field Services, Cantera Natural Gas, Inc., and Cantera Gas Company, were named as defendants in four class action lawsuits and one individual lawsuit arising as a result of alleged inaccurate natural gas price reporting to publications that report trade information. Allegations include price‑fixing conspiracies, restraint of trade, and artificial inflation of natural gas retail prices in Kansas, Missouri, and Wisconsin. In 2016, CMS Energy entities reached a settlement with the plaintiffs in the Kansas and Missouri class action cases for an amount that was not material to CMS Energy. In 2017, the federal district court approved the settlement. Plaintiffs made claims for treble damages, full consideration damages, exemplary damages, costs, interest, and/or attorneys’ fees.

After removal to federal court, all of the cases were transferred to a single federal district court pursuant to the multidistrict litigation process. In 2010 and 2011, all claims against CMS Energy defendants were dismissed by the district court based on FERC preemption.

In 2013, the U.S. Court of Appeals for the Ninth Circuit reversed the district court decision. The appellate court found that FERC preemption does not apply under the facts of these cases. The appellate court affirmed the district court’s denial of leave to amend to add federal antitrust claims. The matter was appealed to the U.S. Supreme Court, which in 2015 upheld the Ninth Circuit’s decision. The cases were remanded back to the federal district court.

In 2016, the federal district court granted the defendants’ motion for summary judgment in the individual lawsuit filed in Kansas based on a release in a prior settlement involving similar allegations; the order of summary judgment was subsequently appealed. In 2018, the U.S. Court of Appeals for the Ninth Circuit reversed the lower court’s ruling and remanded the case back to the federal district court.

In 2017, the federal district court denied plaintiffs’ motion for class certification in the two pending class action cases in Wisconsin. The plaintiffs appealed that decision to the U.S. Court of Appeals for the Ninth Circuit and in 2018, the Ninth Circuit Court of Appeals reversed and remanded the matter back to the federal district court for further consideration.

In January 2019, the judge in the multidistrict litigation granted motions filed by plaintiffs for Suggestion of Remand of the actions back to the respective transferor courts in Wisconsin and Kansas for further handling. In the Kansas action, the Judicial Panel on Multidistrict Litigation ordered the remand and the case has been transferred. In the Wisconsin actions, oppositions to the remand were filed, but the Judicial Panel on Multidistrict Litigation granted the remand in June 2019.

In 2019, CMS Energy and the plaintiffs in each of the Kansas and the Wisconsin actions engaged in settlement discussions and CMS Energy recorded a $30 million liability at December 31, 2019 as the probable estimate to settle the two cases. The parties executed a settlement agreement in the Kansas case in February 2020, and that case is now complete. In the Wisconsin case, a settlement agreement was approved in August 2020 and that case is now complete.

Bay Harbor: CMS Land retained environmental remediation obligations for the collection and treatment of leachate at Bay Harbor after selling its interests in the development in 2002. Leachate is produced when water enters into cement kiln dust piles left over from former cement plant operations at the site. In 2012, CMS Land and EGLE finalized an agreement that established the final remedies and the future water quality criteria at the site. CMS Land completed all construction necessary to implement the remedies required by the agreement and will continue to maintain and operate a system to discharge treated leachate into Little Traverse Bay under an NPDES permit, which is valid through September 2020.

CMS Land submitted a renewal request for the permit in April 2020. CMS Land is allowed to continue operating under the previous NPDES permit until a response is received from EGLE.

At September 30, 2020, CMS Energy had a recorded liability of $44 million for its remaining obligations for environmental remediation. CMS Energy calculated this liability based on discounted projected costs, using a discount rate of 4.34 percent and an inflation rate of one percent on annual operating and maintenance costs. The undiscounted amount of the remaining obligation is $55 million. CMS Energy expects to pay the following amounts for long‑term leachate disposal and operating and maintenance costs during the remainder of 2020 and in each of the next five years:



In Millions
	2020			2021			2022			2023			2024			2025
CMS Energy
Long‑term leachate disposal and operating and maintenance costs		$	1		$	4		$	4		$	4		$	4		$	4

CMS Energy’s estimate of response activity costs and the timing of expenditures could change if there are changes in circumstances or assumptions used in calculating the liability. Although a liability for its present estimate of remaining response activity costs has been recorded, CMS Energy cannot predict the ultimate financial impact or outcome of this matter.

Equatorial Guinea Tax Claim: In 2002, CMS Energy sold its oil, gas, and methanol investments in Equatorial Guinea. The government of Equatorial Guinea claims that, in connection with the sale, CMS Energy owes $152 million in taxes, plus substantial penalties and interest that could be up to or exceed the amount of the taxes claimed. In 2015, the matter was proceeding to formal arbitration; however, since then, the government of Equatorial Guinea has stopped communicating. CMS Energy has concluded that the government’s tax claim is without merit and will continue to contest the claim, but cannot predict the financial impact or outcome of the matter. An unfavorable outcome could have a material adverse effect on CMS Energy’s liquidity, financial condition, and results of operations.

Consumers Electric Utility Contingencies

Electric Environmental Matters: Consumers’ operations are subject to environmental laws and regulations. Historically, Consumers has generally been able to recover, in customer rates, the costs to operate its facilities in compliance with these laws and regulations.

Cleanup and Solid Waste: Consumers expects to incur remediation and other response activity costs at a number of sites under the NREPA. Consumers believes that these costs should be recoverable in rates, but cannot guarantee that outcome. Consumers estimates that its liability for NREPA sites for which it can estimate a range of loss will be between $3 million and $4 million. At September 30, 2020, Consumers had a recorded liability of $3 million, the minimum amount in the range of its estimated probable NREPA liability, as no amount in the range was considered a better estimate than any other amount.

Consumers is a potentially responsible party at a number of contaminated sites administered under CERCLA. CERCLA liability is joint and several. In 2010, Consumers received official notification from the EPA that identified Consumers as a potentially responsible party for cleanup of PCBs at the Kalamazoo River CERCLA site. The notification claimed that the EPA has reason to believe that Consumers disposed of PCBs and arranged for the disposal and treatment of PCB‑containing materials at portions of the site. In 2011, Consumers received a follow‑up letter from the EPA requesting that Consumers agree to participate in a removal action plan along with several other companies for an area of lower Portage Creek, which is connected to the Kalamazoo River. All parties, including Consumers, that were asked to participate in the removal action plan declined to accept liability. Until further information

is received from the EPA, Consumers is unable to estimate a range of potential liability for cleanup of the river.

Based on its experience, Consumers estimates that its share of the total liability for known CERCLA sites will be between $3 million and $8 million. Various factors, including the number and creditworthiness of potentially responsible parties involved with each site, affect Consumers’ share of the total liability. At September 30, 2020, Consumers had a recorded liability of $3 million for its share of the total liability at these sites, the minimum amount in the range of its estimated probable CERCLA liability, as no amount in the range was considered a better estimate than any other amount.

The timing of payments related to Consumers’ remediation and other response activities at its CERCLA and NREPA sites is uncertain. Consumers periodically reviews these cost estimates. A change in the underlying assumptions, such as an increase in the number of sites, different remediation techniques, the nature and extent of contamination, and legal and regulatory requirements, could affect its estimates of NREPA and CERCLA liability.

Ludington PCB: In 1998, during routine maintenance activities, Consumers identified PCB as a component in certain paint, grout, and sealant materials at the Ludington pumped-storage plant. Consumers removed part of the PCB material and replaced it with non‑PCB material. Consumers has had several communications with the EPA regarding this matter, but cannot predict the financial impact or outcome.

MCV PPA: In 2017, the MCV Partnership initiated arbitration against Consumers, asserting a breach of contract associated with the MCV PPA. Under this PPA, Consumers pays the MCV Partnership a fixed energy charge based on Consumers’ annual average baseload coal generating plant operating and maintenance cost, fuel inventory, and administrative and general expenses. The MCV Partnership asserts that, under the Clean Air Act, Consumers should have installed pollution control equipment on coal‑fueled electric generating units years before they were retired. The MCV Partnership also asserts that Consumers should have installed pollution control equipment earlier on its remaining coal‑fueled electric generating units. Additionally, the MCV Partnership claims that Consumers improperly characterized certain costs included in the calculation of the fixed energy charge.

In January 2019, an arbitration panel issued an order concluding that the MCV Partnership is not entitled to any damages associated with its claim against Consumers related to the Clean Air Act; the majority of the MCV Partnership’s claim, which estimated damages and interest in excess of $270 million, was related to this dismissed claim. In April 2020, the MCV Partnership and Consumers signed a term sheet outlining a settlement in principle of all outstanding disputes between the parties. The settlement and associated agreements will require MPSC approval. Once those are approved, the parties will dismiss this matter with prejudice. If settlement is not approved, the arbitration panel will issue an order. Consumers believes that the MCV Partnership’s claims are without merit, but cannot predict the financial impact or outcome of the matter.

Underwater Cables in Straits of Mackinac: Consumers owns certain underwater electric cables in the Straits of Mackinac, which were de‑energized and retired in 1990. Consumers was notified that some of these cables were damaged as a result of vessel activity in 2018. Following the notification, Consumers located, inspected, sampled, capped, and returned the damaged retired cables to their original location on the lake bottom, and did not find any substantive evidence of environmental contamination. After collaborating with the State of Michigan, local Native American tribes, and other stakeholders, Consumers submitted a permit application and removal work plan with EGLE and the U.S. Army Corps of Engineers in December 2019 for partial removal of all Consumers-owned cables. In March 2020, EGLE issued a permit for the removal work and, as a result, Consumers recorded an ARO liability of

$5 million for the cost to remove partially its cables. Removal work was completed in September 2020. Consumers recovers the cost of recorded AROs through MPSC-approved depreciation rates.

Consumers Gas Utility Contingencies

Gas Environmental Matters: Consumers expects to incur remediation and other response activity costs at a number of sites under the NREPA. These sites include 23 former MGP facilities. Consumers operated the facilities on these sites for some part of their operating lives. For some of these sites, Consumers has no present ownership interest or may own only a portion of the original site.

At September 30, 2020, Consumers had a recorded liability of $57 million for its remaining obligations for these sites. This amount represents the present value of long‑term projected costs, using a discount rate of 2.57 percent and an inflation rate of 2.5 percent. The undiscounted amount of the remaining obligation is $62 million. Consumers expects to pay the following amounts for remediation and other response activity costs during the remainder of 2020 and in each of the next five years:



In Millions
	2020			2021			2022			2023			2024			2025
Consumers
Remediation and other response activity costs		$	1		$	2		$	8		$	23		$	10		$	1

Consumers periodically reviews these cost estimates. Any significant change in the underlying assumptions, such as an increase in the number of sites, changes in remediation techniques, or legal and regulatory requirements, could affect Consumers’ estimates of annual response activity costs and the MGP liability.

Pursuant to orders issued by the MPSC, Consumers defers its MGP‑related remediation costs and recovers them from its customers over a ten‑year period. At September 30, 2020, Consumers had a regulatory asset of $122 million related to the MGP sites.

Consumers estimates that its liability to perform remediation and other response activities at NREPA sites other than the MGP sites could reach $3 million. At September 30, 2020, Consumers had a recorded liability of less than $1 million, the minimum amount in the range of its estimated probable liability, as no amount in the range was considered a better estimate than any other amount.

Ray Compressor Station: On January 30, 2019, Consumers experienced a fire at the Ray Compressor Station, which resulted in the Ray Storage Field being off‑line or operating at significantly reduced capacity, which negatively affected Consumers’ natural gas supply and delivery capacity. This incident, which occurred during the extreme polar vortex weather condition, required Consumers to request voluntary reductions in customer load, to implement contingency gas supply purchases, and to implement a curtailment of natural gas deliveries for industrial and large commercial customers pursuant to Consumers’ MPSC curtailment tariff. The curtailment and request for voluntary reductions of customer loads were canceled as of midnight, February 1, 2019. Consumers investigated the cause of the incident, and filed a report on the incident with the MPSC in April 2019. In response, the MPSC issued an order in July 2019, directing Consumers to file additional reports regarding the incident and to include detail of the resulting costs in a future rate proceeding. The compressor station is presently operating at full capacity.

In September 2020, the MPSC disallowed the recovery of $7 million in incremental gas purchases related to the fire. Consumers could be subject to disallowances of costs associated with the repair and

modification of the Ray Compressor Station. At September 30, 2020, Consumers had incurred capital expenditures of $17 million to restore and modify the compressor station.

In May 2020, the MPSC approved an administrative settlement agreement between Consumers and the MPSC Staff, which resulted in a $10,000 civil penalty in connection with the fire. Consumers may also be subject to various claims from impacted customers and claims for damages. At this time, Consumers cannot predict the outcome of these matters or other gas-related incidents and a reasonable estimate of a total loss cannot be made, but they could have a material adverse effect on Consumers’ results of operations, financial condition, or liquidity, and could subject Consumers’ gas utility to increased regulatory scrutiny.

Guarantees

Presented in the following table are CMS Energy’s and Consumers’ guarantees at September 30, 2020:



In Millions
Guarantee Description	Issue Date	Expiration Date	Maximum Obligation			Carrying Amount
CMS Energy, including Consumers
Indemnity obligations from stock and asset sale agreements¹	various	indefinite		$	153		$	2
Guarantee²	July 2011	indefinite		30			—
Consumers
Guarantee²	July 2011	indefinite		$	30		$	—

¹

These obligations arose from stock and asset sale agreements under which CMS Energy or a subsidiary of CMS Energy indemnified the purchaser for losses resulting from various matters, primarily claims related to taxes. The maximum obligation amount is mostly related to the Equatorial Guinea tax claim discussed in the CMS Energy Contingencies section of this Note. CMS Energy believes the likelihood of material loss to be remote for the indemnity obligations not recorded as liabilities.


²	This obligation comprises a guarantee provided by Consumers to the U.S. Department of Energy in connection with a settlement agreement regarding damages resulting from the department’s failure to accept spent nuclear fuel from nuclear power plants formerly owned by Consumers.

Additionally, in the normal course of business, CMS Energy, Consumers, and certain other subsidiaries of CMS Energy have entered into various agreements containing tax and other indemnity provisions for which they are unable to estimate the maximum potential obligation. The carrying value of these indemnity obligations is $1 million. CMS Energy and Consumers consider the likelihood that they would be required to perform or incur substantial losses related to these indemnities to be remote.

Other Contingencies

In addition to the matters disclosed in this Note and Note 2, Regulatory Matters, there are certain other lawsuits and administrative proceedings before various courts and governmental agencies, as well as unasserted claims that may result in such proceedings, arising in the ordinary course of business to which CMS Energy, Consumers, and certain other subsidiaries of CMS Energy are parties. These other lawsuits, proceedings, and unasserted claims may involve personal injury, property damage, contracts, environmental matters, federal and state taxes, rates, licensing, employment, and other matters. Further, CMS Energy and Consumers occasionally self‑report certain regulatory non‑compliance matters that may or may not eventually result in administrative proceedings. CMS Energy and Consumers believe that the

outcome of any one of these proceedings and potential claims will not have a material negative effect on their consolidated results of operations, financial condition, or liquidity.

Consumers Energy Company