ATMOS ENERGY CORP, 10-Q filed on 5/7/2025
Quarterly Report
v3.25.1
Cover Page - shares
 6 Months Ended
Mar. 31, 2025
May 02, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2025  
Document Transition Report false  
Entity File Number 1-10042  
Entity Registrant Name Atmos Energy Corp  
Entity Incorporation, State or Country Code TX  
Entity Tax Identification Number 75-1743247  
Entity Address, Address Line One 1800 Three Lincoln Centre  
Entity Address, Address Line Two 5430 LBJ Freeway  
Entity Address, City or Town Dallas  
Entity Address, State or Province TX  
Entity Address, Postal Zip Code 75240  
City Area Code 972  
Local Phone Number 934-9227  
Title of 12(b) Security Common stock  
Trading Symbol ATO  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding (in shares)   158,836,864
Entity Central Index Key 0000731802  
Current Fiscal Year End Date --09-30  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Amendment Flag false  
v3.25.1
CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Thousands
Mar. 31, 2025
Sep. 30, 2024
ASSETS    
Property, plant and equipment $ 27,451,302 $ 25,848,083
Less accumulated depreciation and amortization 3,819,079 3,643,716
Net property, plant and equipment 23,632,223 22,204,367
Current assets    
Cash and cash equivalents 543,504 307,340
Restricted cash and cash equivalents 1,616 1,516
Cash and cash equivalents and restricted cash and cash equivalents 545,120 308,856
Accounts receivable, net 660,634 365,882
Gas stored underground 97,254 169,508
Other current assets 288,275 288,068
Total current assets 1,591,283 1,132,314
Securitized intangible asset, net (See Note 9) 78,892 82,844
Goodwill 731,257 731,257
Deferred charges and other assets 946,726 1,043,683
Total assets 26,980,381 25,194,465
Shareholders’ equity    
Common stock, no par value (stated at $0.005 per share); 200,000,000 shares authorized; issued and outstanding: March 31, 2025 — 158,835,123 shares; September 30, 2024 — 155,258,845 shares 794 776
Additional paid-in capital 7,880,436 7,474,559
Accumulated other comprehensive income 476,551 465,715
Retained earnings 4,780,184 4,216,619
Shareholders’ equity 13,137,965 12,157,669
Long-term debt, net 8,413,725 7,783,646
Securitized long-term debt (See Note 9) 72,609 76,871
Total capitalization 21,624,299 20,018,186
Current liabilities    
Accounts payable and accrued liabilities 445,225 445,397
Other current liabilities 733,154 750,620
Current maturities of long-term debt 11,712 1,651
Current maturities of securitized long-term debt (See Note 9) 8,418 8,207
Total current liabilities 1,198,509 1,205,875
Deferred income taxes 2,793,163 2,593,342
Regulatory excess deferred taxes 155,169 177,315
Regulatory cost of removal obligation 527,287 507,815
Deferred credits and other liabilities 681,954 691,932
Total capitalization and liabilities $ 26,980,381 $ 25,194,465
v3.25.1
CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares
Mar. 31, 2025
Sep. 30, 2024
Statement of Financial Position [Abstract]    
Common stock stated value (USD per share) $ 0.005 $ 0.005
Common stock authorized (in shares) 200,000,000 200,000,000
Common stock issued (in shares) 158,835,123 155,258,845
Common stock outstanding (in shares) 158,835,123 155,258,845
v3.25.1
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($)
shares in Thousands, $ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Operating revenues $ 1,950,502 $ 1,647,227 $ 3,126,501 $ 2,805,694
Purchased gas cost 779,233 624,295 1,013,281 963,164
Operation and maintenance expense 233,296 199,899 440,340 366,244
Depreciation and amortization expense 182,750 165,087 363,283 329,695
Taxes, other than income 126,284 106,956 221,178 196,496
Operating income 628,939 550,990 1,088,419 950,095
Other non-operating income 24,172 16,687 48,806 34,573
Interest charges 50,014 55,442 102,939 107,317
Income before income taxes 603,097 512,235 1,034,286 877,351
Income tax expense 117,521 80,212 196,852 134,036
Net income $ 485,576 $ 432,023 $ 837,434 $ 743,315
Basic net income per share (USD per share) $ 3.05 $ 2.85 $ 5.31 $ 4.93
Diluted net income per share (USD per share) 3.03 2.85 5.26 4.93
Cash dividends per share (USD per share) $ 0.870 $ 0.805 $ 1.74 $ 1.61
Basic weighted average shares outstanding (in shares) 159,177 151,271 157,739 150,534
Diluted weighted average shares outstanding (in shares) 160,426 151,297 159,125 150,547
Other comprehensive income (loss), net of tax        
Net unrealized holding gains (losses) on available-for-sale securities, net of tax of $20 and $(15) $ 73 $ (50) $ (65) $ 246
Cash flow hedges:        
Amortization and unrealized gains (losses) on interest rate agreements, net of tax of $(1,622) and $7,850 (5,660) 27,158 10,901 (23,074)
Total other comprehensive income (loss) (5,587) 27,108 10,836 (22,828)
Total comprehensive income 479,989 459,131 848,270 720,487
Distribution segment        
Operating revenues 1,881,742 1,588,394 2,990,311 2,693,013
Pipeline and storage segment        
Operating revenues 68,760 58,833 136,190 112,681
Operating Segments | Distribution segment        
Operating revenues 1,882,528 1,589,181 2,991,863 2,694,519
Purchased gas cost 969,037 788,643 1,391,607 1,285,305
Operation and maintenance expense 181,887 154,956 336,401 282,571
Depreciation and amortization expense 134,546 121,384 268,173 241,069
Taxes, other than income 113,340 98,008 195,916 178,903
Operating income 483,718 426,190 799,766 706,671
Other non-operating income 13,444 9,359 23,528 15,198
Interest charges 30,087 36,784 64,336 71,365
Income before income taxes 467,075 398,765 758,958 650,504
Income tax expense 86,432 56,073 138,102 86,375
Net income 380,643 342,692 620,856 564,129
Operating Segments | Pipeline and storage segment        
Operating revenues 258,999 223,487 514,389 434,656
Purchased gas cost 968 840 910 844
Operation and maintenance expense 51,662 45,196 104,454 84,169
Depreciation and amortization expense 48,204 43,703 95,110 88,626
Taxes, other than income 12,944 8,948 25,262 17,593
Operating income 145,221 124,800 288,653 243,424
Other non-operating income 10,728 7,328 25,278 19,375
Interest charges 19,927 18,658 38,603 35,952
Income before income taxes 136,022 113,470 275,328 226,847
Income tax expense 31,089 24,139 58,750 47,661
Net income 104,933 89,331 216,578 179,186
Eliminations        
Operating revenues (191,025) (165,441) (379,751) (323,481)
Purchased gas cost (190,772) (165,188) (379,236) (322,985)
Operation and maintenance expense (253) (253) (515) (496)
Depreciation and amortization expense 0 0 0 0
Taxes, other than income 0 0 0 0
Operating income 0 0 0 0
Other non-operating income 0 0 0 0
Interest charges 0 0 0 0
Income before income taxes 0 0 0 0
Income tax expense 0 0 0 0
Net income 0 0 0 0
Eliminations | Distribution segment        
Operating revenues (786) (787) (1,552) (1,506)
Eliminations | Pipeline and storage segment        
Operating revenues $ (190,239) $ (164,654) $ (378,199) $ (321,975)
v3.25.1
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Income Statement [Abstract]        
Net unrealized holding gains (losses) on available-for-sale securities, tax $ 20 $ (15) $ (22) $ 71
Amortization and unrealized gains (losses) on interest rate agreements, net $ (1,622) $ 7,850 $ 1,870 $ (6,669)
v3.25.1
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Thousands
 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Cash Flows From Operating Activities    
Net income $ 837,434 $ 743,315
Adjustments to reconcile net income to net cash provided by operating activities:    
Depreciation and amortization expense 363,283 329,695
Deferred income taxes 170,965 110,098
Other (32,691) (28,023)
Net assets / liabilities from risk management activities 845 1,683
Net change in other operating assets and liabilities (134,877) (164,895)
Net cash provided by operating activities 1,204,959 991,873
Cash Flows From Investing Activities    
Capital expenditures (1,730,857) (1,415,526)
Debt and equity securities activities, net 710 (1,010)
Other, net 12,609 7,272
Net cash used in investing activities (1,717,538) (1,409,264)
Cash Flows From Financing Activities    
Net decrease in short-term debt 0 (241,933)
Net proceeds from equity issuances 379,490 254,022
Issuance of common stock through stock purchase and employee retirement plans 7,888 7,771
Proceeds from issuance of long-term debt 645,372 898,275
Repayment of securitized long-term debt by AEK (4,051) (5,738)
Cash dividends paid (273,869) (241,565)
Debt issuance costs (5,987) (8,920)
Net cash provided by financing activities 748,843 661,912
Net increase in cash and cash equivalents and restricted cash and cash equivalents 236,264 244,521
Cash and cash equivalents and restricted cash and cash equivalents at beginning of period 308,856 19,248
Cash and cash equivalents and restricted cash and cash equivalents at end of period $ 545,120 $ 263,769
v3.25.1
Nature of Business
 6 Months Ended
Mar. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Nature of Business Nature of Business
Atmos Energy Corporation (“Atmos Energy” or the “Company”) and its subsidiaries are engaged in the regulated natural gas distribution and pipeline and storage businesses. Our distribution business is subject to federal and state regulation and/or regulation by local authorities in each of the states in which our regulated divisions and subsidiaries operate.
Our distribution business delivers natural gas through sales and transportation arrangements to over 3.3 million residential, commercial, public authority, and industrial customers through our six regulated distribution divisions, which at March 31, 2025, covered service areas located in eight states.
Our pipeline and storage business, which is also subject to federal and state regulations, includes the transportation of natural gas to our Texas and Louisiana distribution systems and the management of our underground storage facilities used to support our distribution business in various states.
v3.25.1
Summary of Significant Accounting Policies
 6 Months Ended
Mar. 31, 2025
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies Summary of Significant Accounting Policies
Basis of Presentation
These consolidated interim-period financial statements have been prepared in accordance with accounting principles generally accepted in the United States on the same basis as those used for the Company’s audited consolidated financial statements included in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024. In the opinion of management, all material adjustments (consisting of normal recurring accruals) necessary for a fair presentation have been made to the unaudited consolidated interim-period financial statements. These consolidated interim-period financial statements are condensed as permitted by the instructions to Form 10-Q and should be read in conjunction with the audited consolidated financial statements of Atmos Energy Corporation included in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024. Because of seasonal and other factors, the results of operations for the six-month period ended March 31, 2025 are not indicative of our results of operations for the full 2025 fiscal year, which ends September 30, 2025.
Significant accounting policies
Our accounting policies are described in Note 2 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024.
During the second quarter of fiscal 2025, we completed our annual goodwill impairment assessment using a qualitative assessment, as permitted under U.S. GAAP. We test for goodwill at the reporting unit level on an annual basis and between annual tests if an event occurs or circumstances change that would more likely than not reduce the fair value of the reporting unit. Based on the assessment performed, we determined that our goodwill was not impaired.
No events have occurred subsequent to the balance sheet date that would require recognition or disclosure in the condensed consolidated financial statements.
Recently issued accounting pronouncements
In November 2023, the Financial Accounting Standards Board (FASB) issued guidance which provides updates to qualitative and quantitative reportable segment disclosure requirements, including enhanced disclosures about significant segment expenses and increased interim disclosure requirements, among others. The amendment is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted, and the amendments should be applied retrospectively. This amendment will be effective for our Form 10-K for fiscal 2025 and our Form 10-Q for the first quarter of fiscal 2026. We are currently evaluating the impact this may have on our financial statement disclosures.
In December 2023, the FASB issued guidance which provides qualitative and quantitative updates to the rate reconciliation and income taxes paid disclosures, among others, in order to enhance the transparency of income tax disclosures, including consistent categories and greater disaggregation of information in the rate reconciliation and disaggregation by jurisdiction of income taxes paid. The amendment is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. The amendments should be applied prospectively; however, retrospective application is also permitted. This amendment will be effective for our Form 10-K for fiscal 2026. We are currently evaluating the impact this amendment may have on our financial statement disclosures.
In November 2024, the FASB issued guidance that will require more detailed information about the types of expenses in commonly presented expense captions. The amendment is effective for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. This amendment will be effective for our Form 10-K for fiscal 2028 and our Form 10-Q for the first quarter of fiscal 2029. We are currently evaluating the impact this may have on our financial statement disclosures.
v3.25.1
Regulation
 6 Months Ended
Mar. 31, 2025
Regulated Operations [Abstract]  
Regulation Regulation
Accounting principles generally accepted in the United States require cost-based, rate-regulated entities that meet certain criteria to reflect the authorized recovery of costs due to regulatory decisions in their financial statements. As a result, certain costs are permitted to be capitalized rather than expensed because they can be recovered through rates. We record certain costs as regulatory assets when future recovery through customer rates is considered probable. Regulatory liabilities are recorded when it is probable that revenues will be reduced for amounts that will be credited to customers through the ratemaking process. Substantially all of our regulatory assets are recorded as a component of other current assets and deferred charges and other assets and our regulatory liabilities are recorded as a component of other current liabilities and deferred credits and other liabilities. Deferred gas costs are recorded either in other current assets or liabilities.
Regulatory assets and liabilities as of March 31, 2025 and September 30, 2024 included the following:
March 31,
2025		September 30,
2024
 (In thousands)
Regulatory assets:
Pension and postretirement benefit costs$4,326 $11,243 
Infrastructure mechanisms (1)
239,997 246,734 
Winter Storm Uri incremental costs6,812 10,373 
Deferred gas costs3,830 159,762 
Regulatory excess deferred taxes (2)
50,526 51,380 
Recoverable loss on reacquired debt2,987 3,070 
Deferred pipeline record collection costs39,899 41,742 
APT annual System Safety and Integrity Rider (3)
34,142 38,632 
Other16,270 16,454 
$398,789 $579,390 
Regulatory liabilities:
Regulatory excess deferred taxes (2)
$229,096 $257,001 
Regulatory cost of removal obligation625,899 607,032 
Deferred gas costs54,794 9,142 
APT annual adjustment mechanism78,126 73,119 
Pension and postretirement benefit costs236,382 247,250 
Other51,006 34,338 
$1,275,303 $1,227,882 
 
(1)Infrastructure mechanisms in Texas, Louisiana, and Tennessee allow for the deferral of all eligible expenses associated with capital expenditures incurred pursuant to these rules, including the recording of interest on deferred expenses until the next rate proceeding (rate case or annual rate filing), at which time investment and costs would be recoverable through base rates.
(2)Regulatory excess deferred taxes represent changes in our net deferred tax liability related to our cost of service ratemaking due to the enactment of Tax Cuts and Jobs Act of 2017 (the "TCJA"), a Kansas legislative change enacted in fiscal 2020, and a Louisiana legislative change enacted in fiscal 2025. See Note 12 to the condensed consolidated financial statements for further information.
(3)In APT's general rate case settlement in December 2023, the RRC approved a new annual compliance filing that allows APT to recover certain system safety and integrity costs incurred each year. Costs above a specified benchmark are deferred onto the balance sheet as incurred. Once the filing is approved by the RRC, the revenue and expense are recognized over 12 months resulting in no impact to operating income.
We deferred $32.4 million in carrying costs incurred after September 1, 2022 associated with interim financing for gas costs incurred in February 2021 during Winter Storm Uri. During fiscal 2024, we recovered $22.0 million of this amount. During the first six months of fiscal 2025, we have recovered $3.6 million of this amount. Of the remaining $6.8 million,
$0.4 million has been recorded as a current asset in other current assets as of March 31, 2025 and $6.4 million has been recorded as a long-term asset in deferred charges and other assets as of March 31, 2025 as we anticipate recovering this amount in future regulatory proceedings.
v3.25.1
Segment Information
 6 Months Ended
Mar. 31, 2025
Segment Reporting [Abstract]  
Segment Information Segment Information
We manage and review our consolidated operations through the following reportable segments:

•The distribution segment is comprised of our regulated natural gas distribution and related sales operations in eight states.
•The pipeline and storage segment is comprised primarily of the regulated pipeline and storage operations of our Atmos Pipeline-Texas division and our natural gas transmission operations in Louisiana.
The accounting policies of the segments are the same as those described in the summary of significant accounting policies found in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024.
Income statements and capital expenditures for the three and six months ended March 31, 2025 and 2024 by segment are presented in the following tables:
 Three Months Ended March 31, 2025
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Operating revenues from external parties$1,881,742 $68,760 $— $1,950,502 
Intersegment revenues786 190,239 (191,025)— 
Total operating revenues1,882,528 258,999 (191,025)1,950,502 
Purchased gas cost
969,037 968 (190,772)779,233 
Operation and maintenance expense181,887 51,662 (253)233,296 
Depreciation and amortization expense134,546 48,204 — 182,750 
Taxes, other than income113,340 12,944 — 126,284 
Operating income483,718 145,221 — 628,939 
Other non-operating income13,444 10,728 — 24,172 
Interest charges30,087 19,927 — 50,014 
Income before income taxes
467,075 136,022 — 603,097 
Income tax expense86,432 31,089 — 117,521 
Net income$380,643 $104,933 $— $485,576 
Capital expenditures$594,853 $244,813 $— $839,666 
 Three Months Ended March 31, 2024
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Operating revenues from external parties$1,588,394 $58,833 $— $1,647,227 
Intersegment revenues787 164,654 (165,441)— 
Total operating revenues1,589,181 223,487 (165,441)1,647,227 
Purchased gas cost
788,643 840 (165,188)624,295 
Operation and maintenance expense154,956 45,196 (253)199,899 
Depreciation and amortization expense121,384 43,703 — 165,087 
Taxes, other than income98,008 8,948 — 106,956 
Operating income426,190 124,800 — 550,990 
Other non-operating income9,359 7,328 — 16,687 
Interest charges36,784 18,658 — 55,442 
Income before income taxes
398,765 113,470 — 512,235 
Income tax expense56,073 24,139 — 80,212 
Net income$342,692 $89,331 $— $432,023 
Capital expenditures$532,997 $112,879 $— $645,876 
 Six Months Ended March 31, 2025
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Operating revenues from external parties$2,990,311 $136,190 $— $3,126,501 
Intersegment revenues1,552 378,199 (379,751)— 
Total operating revenues2,991,863 514,389 (379,751)3,126,501 
Purchased gas cost
1,391,607 910 (379,236)1,013,281 
Operation and maintenance expense336,401 104,454 (515)440,340 
Depreciation and amortization expense268,173 95,110 — 363,283 
Taxes, other than income195,916 25,262 — 221,178 
Operating income799,766 288,653 — 1,088,419 
Other non-operating income23,528 25,278 — 48,806 
Interest charges64,336 38,603 — 102,939 
Income before income taxes
758,958 275,328 — 1,034,286 
Income tax expense138,102 58,750 — 196,852 
Net income$620,856 $216,578 $— $837,434 
Capital expenditures$1,220,502 $510,355 $— $1,730,857 
 Six Months Ended March 31, 2024
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Operating revenues from external parties$2,693,013 $112,681 $— $2,805,694 
Intersegment revenues1,506 321,975 (323,481)— 
Total operating revenues2,694,519 434,656 (323,481)2,805,694 
Purchased gas cost
1,285,305 844 (322,985)963,164 
Operation and maintenance expense282,571 84,169 (496)366,244 
Depreciation and amortization expense241,069 88,626 — 329,695 
Taxes, other than income178,903 17,593 — 196,496 
Operating income706,671 243,424 — 950,095 
Other non-operating income15,198 19,375 — 34,573 
Interest charges71,365 35,952 — 107,317 
Income before income taxes
650,504 226,847 — 877,351 
Income tax expense86,375 47,661 — 134,036 
Net income$564,129 $179,186 $— $743,315 
Capital expenditures$1,072,155 $343,371 $— $1,415,526 
Balance sheet information at March 31, 2025 and September 30, 2024 by segment is presented in the following tables:
 March 31, 2025
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Net property, plant and equipment$17,422,364 $6,209,859 $— $23,632,223 
Total assets$26,109,156 $6,541,506 $(5,670,281)$26,980,381 
 September 30, 2024
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Net property, plant and equipment$16,372,659 $5,831,708 $— $22,204,367 
Total assets$24,328,877 $6,181,558 $(5,315,970)$25,194,465 
v3.25.1
Earnings Per Share
 6 Months Ended
Mar. 31, 2025
Earnings Per Share [Abstract]  
Earnings Per Share Earnings Per Share
We use the two-class method of computing earnings per share because we have participating securities in the form of non-vested restricted stock units with a nonforfeitable right to dividend equivalents, for which vesting is predicated solely on the passage of time. The calculation of earnings per share using the two-class method excludes income attributable to these participating securities from the numerator and excludes the dilutive impact of those shares from the denominator. Basic weighted average shares outstanding is calculated based upon the weighted average number of common shares outstanding during the periods presented. Also, this calculation includes fully vested stock awards that have not yet been issued as common stock. Additionally, the weighted average shares outstanding for diluted EPS includes the incremental effects of the forward sale agreements, discussed in Note 8 to the condensed consolidated financial statements, when the impact is dilutive.
Basic and diluted earnings per share for the three and six months ended March 31, 2025 and 2024 are calculated as follows:
 Three Months Ended March 31Six Months Ended March 31
 2025202420252024
 (In thousands, except per share amounts)
Basic Earnings Per Share
Net income$485,576 $432,023 $837,434 $743,315 
Less: Income allocated to participating securities
245 255 436 442 
Income available to common shareholders
$485,331 $431,768 $836,998 $742,873 
Basic weighted average shares outstanding
159,177 151,271 157,739 150,534 
Net income per share — Basic
$3.05 $2.85 $5.31 $4.93 
Diluted Earnings Per Share
Income available to common shareholders$485,331 $431,768 $836,998 $742,873 
Effect of dilutive shares
— — — — 
Income available to common shareholders
$485,331 $431,768 $836,998 $742,873 
Basic weighted average shares outstanding
159,177 151,271 157,739 150,534 
Dilutive shares1,249 26 1,386 13 
Diluted weighted average shares outstanding
160,426 151,297 159,125 150,547 
Net income per share — Diluted$3.03 $2.85 $5.26 $4.93 
v3.25.1
Revenue and Accounts Receivable
 6 Months Ended
Mar. 31, 2025
Revenue from Contract with Customer [Abstract]  
Revenue and Accounts Receivable Revenue and Accounts Receivable
Revenue
Our revenue recognition policy is fully described in Note 2 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024. The following tables disaggregate our revenue from contracts with customers by customer type and segment and provide a reconciliation to total operating revenues, including intersegment revenues, for the three and six months ended March 31, 2025 and 2024.
Three Months Ended March 31, 2025Three Months Ended March 31, 2024
DistributionPipeline and StorageDistributionPipeline and Storage
(In thousands)
Gas sales revenues:
Residential$1,308,691 $— $1,065,296 $— 
Commercial480,108 — 404,701 — 
Industrial38,885 — 30,419 — 
Public authority and other23,921 — 21,120 — 
Total gas sales revenues1,851,605 — 1,521,536 — 
Transportation revenues43,352 266,514 37,607 223,159 
Miscellaneous revenues4,222 4,259 3,724 2,162 
Revenues from contracts with customers1,899,179 270,773 1,562,867 225,321 
Alternative revenue program revenues(20,117)(11,774)22,315 (1,834)
Other revenues3,466 — 3,999 — 
Total operating revenues$1,882,528 $258,999 $1,589,181 $223,487 
Six Months Ended March 31, 2025Six Months Ended March 31, 2024
DistributionPipeline and StorageDistributionPipeline and Storage
(In thousands)
Gas sales revenues:
Residential$2,001,741 $— $1,792,978 $— 
Commercial746,162 — 681,954 — 
Industrial65,206 — 58,650 — 
Public authority and other36,802 — 35,704 — 
Total gas sales revenues2,849,911 — 2,569,286 — 
Transportation revenues80,079 532,543 71,374 438,464 
Miscellaneous revenues7,244 6,923 6,367 5,204 
Revenues from contracts with customers2,937,234 539,466 2,647,027 443,668 
Alternative revenue program revenues47,219 (25,077)39,716 (9,012)
Other revenues7,410 — 7,776 — 
Total operating revenues$2,991,863 $514,389 $2,694,519 $434,656 
We have alternative revenue programs in each of our segments. In our distribution segment, we have weather-normalization adjustment mechanisms that serve to mitigate the effects of weather on our revenue. In our pipeline and storage segment, APT has a regulatory mechanism that requires that we share with its tariffed customers 75% of the difference between the total non-tariffed revenues earned during a test period and a revenue benchmark established by the RRC. Other revenues includes AEK revenues (see Note 9 to the condensed consolidated financial statements) and other miscellaneous revenues.
Accounts receivable and allowance for uncollectible accounts
Accounts receivable arise from natural gas sales to residential, commercial, industrial, public authority, and other customers. Our accounts receivable balance includes unbilled amounts which represent a customer’s consumption of gas from the date of the last cycle billing through the last day of the month. Our policy related to the accounting for our accounts receivable and allowance for uncollectible accounts is fully described in Note 2 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024. During the six months ended March 31, 2025, there were no material changes to this policy. Rollforwards of our allowance for uncollectible accounts for the three and six months ended March 31, 2025 and 2024 are presented in the table below. The allowance excludes the gas cost portion of customers’ bills for approximately 89 percent of our customers as we have the ability to collect these gas costs through our gas cost recovery mechanisms in most of our jurisdictions.
In December 2023, the Mississippi Public Service Commission approved the recovery of uncollectible accounts through our purchased gas cost mechanism over a two-year period rather than through our annual filing mechanism over a one-year period. As a result of this decision, we recorded a $13.9 million reduction to bad debt expense during the first quarter of fiscal 2024. Of this amount, $9.7 million represents future recovery of customer receivables previously written off since April 2022 but not yet recovered through our rates. This amount increased our deferred gas cost regulatory asset. The remaining $4.2 million reduction represents a reversal of our allowance for uncollectible accounts for customer balances that have not yet been written off.
 Three Months Ended March 31, 2025
 (In thousands)
Beginning balance, December 31, 2024$39,166 
Current period provisions14,391 
Write-offs charged against allowance(4,761)
Recoveries of amounts previously written off545 
Ending balance, March 31, 2025
$49,341 
 Three Months Ended March 31, 2024
 (In thousands)
Beginning balance, December 31, 2023$35,406 
Current period provisions12,797 
Write-offs charged against allowance(5,859)
Recoveries of amounts previously written off361 
Ending balance, March 31, 2024
$42,705 
 Six Months Ended March 31, 2025
 (In thousands)
Beginning balance, September 30, 2024
$37,056 
Current period provisions23,015 
Write-offs charged against allowance(12,209)
Recoveries of amounts previously written off1,479 
Ending balance, March 31, 2025
$49,341 
 Six Months Ended March 31, 2024
 (In thousands)
Beginning balance, September 30, 2023
$40,840 
Current period provisions19,547 
Write-offs charged against allowance(14,616)
Recoveries of amounts previously written off1,126 
Mississippi recovery of uncollectible accounts(4,192)
Ending balance, March 31, 2024
$42,705 
v3.25.1
Debt
 6 Months Ended
Mar. 31, 2025
Debt Disclosure [Abstract]  
Debt Debt
The nature and terms of our debt instruments and credit facilities are described in detail in Note 8 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024. Other than as described below, there were no material changes in the terms of our debt instruments during the six months ended March 31, 2025.
Long-term debt at March 31, 2025 and September 30, 2024 consisted of the following:
March 31, 2025September 30, 2024
 (In thousands)
Unsecured 3.00% Senior Notes, due June 2027
$500,000 $500,000 
Unsecured 2.625% Senior Notes, due September 2029
500,000 500,000 
Unsecured 1.50% Senior Notes, due January 2031
600,000 600,000 
Unsecured 5.45% Senior Notes, due October 2032
300,000 300,000 
Unsecured 5.90% Senior Notes, due November 2033

725,000 725,000 
Unsecured 5.95% Senior Notes, due October 2034
200,000 200,000 
Unsecured 5.50% Senior Notes, due June 2041
400,000 400,000 
Unsecured 4.15% Senior Notes, due January 2043
500,000 500,000 
Unsecured 4.125% Senior Notes, due October 2044
750,000 750,000 
Unsecured 4.30% Senior Notes, due October 2048
600,000 600,000 
Unsecured 4.125% Senior Notes, due March 2049
450,000 450,000 
Unsecured 3.375% Senior Notes, due September 2049
500,000 500,000 
Unsecured 2.85% Senior Notes, due February 2052
600,000 600,000 
Unsecured 5.75% Senior Notes, due October 2052
500,000 500,000 
Unsecured 6.20% Senior Notes, due November 2053
500,000 500,000 
Unsecured 5.00% Senior Notes, due December 2054
650,000 — 
Medium-term note Series A, 1995-1, 6.67%, due December 2025
10,000 10,000 
Unsecured 6.75% Debentures, due July 2028
150,000 150,000 
Finance lease obligations48,075 48,890 
Total long-term debt8,483,075 7,833,890 
Less:
Original issue premium on unsecured senior notes and debentures(3,825)(9,071)
Debt issuance cost61,463 57,664 
Current maturities of long-term debt11,712 1,651 
Total long-term debt, net$8,413,725 $7,783,646 
On October 1, 2024, we completed a public offering of $650 million of 5.00% senior notes due December 2054, with an effective interest rate of 3.90%, after giving effect to the offering costs and settlement of our interest rate swaps. The net proceeds from the offering, after the underwriting discount and offering expenses, of $639.4 million were used for general corporate purposes.
Short-term debt
We utilize short-term debt to provide cost-effective, short-term financing until it can be replaced with a balance of long-term debt and equity financing that achieves the Company’s desired capital structure. Our short-term borrowing requirements are driven primarily by construction work in progress and the seasonal nature of the natural gas business.
Our short-term borrowing requirements are satisfied through a combination of a $1.5 billion commercial paper program and four committed revolving credit facilities with third-party lenders that provide $3.1 billion of total working capital funding.
Our commercial paper program is supported by a five-year unsecured $1.5 billion credit facility. On March 31, 2025, we elected to extend the maturity date from March 28, 2029 to March 28, 2030. This facility bears interest at a base rate or at a Term SOFR-based rate for the applicable interest period, plus a margin ranging from zero percent to 0.25 percent for base rate advances or a margin ranging from 0.75 percent to 1.25 percent for Term SOFR-based advances, based on the Company’s credit ratings. Additionally, the facility contains a $250 million accordion feature, which provides the opportunity to increase the total committed loan to $1.75 billion. At March 31, 2025 and September 30, 2024, there were no amounts outstanding under our commercial paper program.
We also have a $1.5 billion three-year unsecured revolving credit facility that is used to provide additional working capital funding. On March 31, 2025, we elected to extend the maturity date from March 28, 2027 to March 28, 2028. This facility bears interest at a base rate or at a Term SOFR-based rate for the applicable interest period, plus a margin ranging from zero percent to 0.25 percent for base rate advances or a margin ranging from 0.75 percent to 1.25 percent for Term SOFR-based advances, based on the Company's credit ratings. Additionally, the facility contains a $250 million accordion feature, which provides the opportunity to increase the total committed loan to $1.75 billion. At March 31, 2025 and September 30, 2024, there were no borrowings outstanding under this facility.
Additionally, we have a $50 million 364-day unsecured facility, which was renewed April 1, 2025 and is used to provide working capital funding. There were no borrowings outstanding under this facility as of March 31, 2025 and September 30, 2024.
Finally, we have a $50 million 364-day unsecured revolving credit facility, which was renewed March 31, 2025 and is used to issue letters of credit and to provide working capital funding. At March 31, 2025, there were no borrowings outstanding under this facility; however, outstanding letters of credit reduced the total amount available to us to $44.4 million.
Debt covenants
The availability of funds under these credit facilities is subject to conditions specified in the respective credit agreements, all of which we currently satisfy. These conditions include our compliance with financial covenants and the continued accuracy of representations and warranties contained in these agreements. We are required by the financial covenants in each of these facilities to maintain, at the end of each fiscal quarter, a ratio of total-debt-to-total-capitalization of no greater than 70 percent. At March 31, 2025, our total-debt-to-total-capitalization ratio, as defined in the agreements, was 40 percent. In addition, both the interest margin and the fee that we pay on unused amounts under certain of these facilities are subject to adjustment depending upon our credit ratings.
These credit facilities and our public indentures contain usual and customary covenants for our business, including covenants substantially limiting liens, substantial asset sales, and mergers. Additionally, our public debt indentures relating to our senior notes and debentures, as well as certain of our revolving credit agreements, each contain a default provision that is triggered if outstanding indebtedness arising out of any other credit agreements in amounts ranging from in excess of $15 million to in excess of $100 million becomes due by acceleration or if not paid at maturity. We were in compliance with all of our debt covenants as of March 31, 2025. If we were unable to comply with our debt covenants, we would likely be required to repay our outstanding balances on demand, provide additional collateral or take other corrective actions.
v3.25.1
Shareholders' Equity
 6 Months Ended
Mar. 31, 2025
Equity [Abstract]  
Shareholders' Equity Shareholders' Equity
The following tables present a reconciliation of changes in stockholders' equity for the three and six months ended March 31, 2025 and 2024.
 Common stockAdditional
Paid-in
Capital		Accumulated
Other
Comprehensive Income
(Loss)		Retained
Earnings		Total
Number of
Shares		Stated
Value
 (In thousands, except share and per share data)
Balance, September 30, 2024
155,258,845 $776 $7,474,559 $465,715 $4,216,619 $12,157,669 
Net income— — — — 351,858 351,858 
Other comprehensive income— — — 16,423 — 16,423 
Cash dividends ($0.87 per share)
— — — — (135,453)(135,453)
Common stock issued:
Public and other stock offerings3,329,358 17 383,520 — — 383,537 
Stock-based compensation plans137,862 1 6,446 — — 6,447 
Balance, December 31, 2024158,726,065 794 7,864,525 482,138 4,433,024 12,780,481 
Net income— — — — 485,576 485,576 
Other comprehensive loss— — — (5,587)— (5,587)
Cash dividends ($0.87 per share)
— — — — (138,416)(138,416)
Common stock issued:
Public and other stock offerings26,367 — 3,841 — — 3,841 
Stock-based compensation plans82,691 — 12,070 — — 12,070 
Balance, March 31, 2025158,835,123 $794 $7,880,436 $476,551 $4,780,184 $13,137,965 
 Common stockAdditional
Paid-in
Capital		Accumulated
Other
Comprehensive Income
(Loss)		Retained
Earnings		Total
Number of
Shares		Stated
Value
 (In thousands, except share and per share data)
Balance, September 30, 2023
148,492,783 $742 $6,684,120 $518,528 $3,666,674 $10,870,064 
Net income— — — — 311,292 311,292 
Other comprehensive loss— — — (49,936)— (49,936)
Cash dividends ($0.805 per share)
— — — — (119,898)(119,898)
Common stock issued:
Public and other stock offerings2,177,864 11 257,757 — — 257,768 
Stock-based compensation plans163,750 1 3,918 — — 3,919 
Balance, December 31, 2023150,834,397 754 6,945,795 468,592 3,858,068 11,273,209 
Net income— — — — 432,023 432,023 
Other comprehensive income— — — 27,108 — 27,108 
Cash dividends ($0.805 per share)
— — — — (121,667)(121,667)
Common stock issued:
Public and other stock offerings34,687 — 4,025 — — 4,025 
Stock-based compensation plans5,468 — 3,941 — — 3,941 
Balance, March 31, 2024150,874,552 $754 $6,953,761 $495,700 $4,168,424 $11,618,639 
Shelf Registration, At-the-Market Equity Sales Program and Equity Issuances
On December 3, 2024, we filed a shelf registration statement with the Securities and Exchange Commission (SEC) that allows us to issue up to $8.0 billion in common stock and/or debt securities, which expires December 3, 2027. At March 31, 2025, $6.3 billion of securities were available for issuance under this shelf registration statement.
On December 3, 2024, we filed a prospectus supplement under the shelf registration statement relating to an at-the-market (ATM) equity sales program under which we may issue and sell shares of our common stock up to an aggregate offering price of $1.7 billion through December 3, 2027 (including shares of common stock that may be sold pursuant to forward sale agreements entered into concurrently with the ATM equity sales program). This ATM equity sales program replaced our previous ATM equity sales program, filed on May 8, 2024.
During the six months ended March 31, 2025, we executed forward sales under our ATM equity sales program with various forward sellers who borrowed and sold 4,609,043 shares of our common stock at an aggregate price of $658.2 million. During the six months ended March 31, 2025, we also settled forward sale agreements with respect to 3,300,904 shares that had been borrowed and sold by various forward sellers under the ATM program for net proceeds of $379.5 million. As of March 31, 2025, $1.0 billion of equity was available for issuance under our existing ATM program. Additionally, we had $1.7 billion in available proceeds from outstanding forward sale agreements, as detailed below.
MaturityShares AvailableNet Proceeds Available
(In thousands)		Forward Price
June 30, 2025630,514 $73,406 $116.42 
September 30, 2025815,655 96,313 $118.08 
December 31, 20252,344,567 297,650 $126.95 
March 31, 20263,627,033 463,284 $127.73 
June 30, 2026669,043 89,150 $133.25 
December 31, 20263,392,352 472,749 $139.36 
March 31, 20271,119,095 $167,073 $149.29 
Total12,598,259 $1,659,625 $131.73 
Accumulated Other Comprehensive Income (Loss)
We record deferred gains (losses) in AOCI related to available-for-sale debt securities and interest rate agreement cash flow hedges. Deferred gains (losses) for our available-for-sale debt securities are recognized in earnings upon settlement, while deferred gains (losses) related to our interest rate agreement cash flow hedges are recognized in earnings on a straight-line basis over the life of the related financing. The following tables provide the components of our accumulated other comprehensive income (loss) balances, net of the related tax effects allocated to each component of other comprehensive income (loss).
Available-
for-Sale
Securities		Interest Rate
Agreement
Cash Flow
Hedges		Total
 (In thousands)
September 30, 2024$213 $465,502 $465,715 
Other comprehensive income (loss) before reclassifications(65)18,041 17,976 
Amounts reclassified from accumulated other comprehensive income— (7,140)(7,140)
Net current-period other comprehensive income (loss)(65)10,901 10,836 
March 31, 2025$148 $476,403 $476,551 
 
Available-
for-Sale
Securities		Interest Rate
Agreement
Cash Flow
Hedges		Total
 (In thousands)
September 30, 2023$(369)$518,897 $518,528 
Other comprehensive income (loss) before reclassifications246 (18,091)(17,845)
Amounts reclassified from accumulated other comprehensive income— (4,983)(4,983)
Net current-period other comprehensive income (loss)246 (23,074)(22,828)
March 31, 2024$(123)$495,823 $495,700 
v3.25.1
Securitization
 6 Months Ended
Mar. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Securitization Securitization
Kansas
Atmos Energy Kansas Securitization I, LLC (AEK), a special-purpose entity wholly owned by Atmos Energy, was formed for the purpose of issuing securitized bonds to recover extraordinary costs incurred during Winter Storm Uri in February 2021. In June 2023, AEK completed a public offering of $95 million of Securitized Utility Tariff Bonds. AEK's assets cannot be used to settle Atmos Energy's obligations, and the holders of the Securitized Utility Tariff Bonds have no recourse against Atmos Energy.
As described in Note 10 of our Annual Report on Form 10-K for the fiscal year ended September 30, 2024, AEK is considered to be a variable interest entity. As a result, AEK is included in the condensed consolidated financial statements of Atmos Energy.
The following table summarizes the impact of AEK on our condensed consolidated balance sheets, for the periods indicated:
March 31, 2025September 30, 2024
 (In thousands)
Restricted cash and cash equivalents$1,616 $1,516 
Other current assets$3 $3 
Securitized intangible asset, net$78,892 $82,844 
Accrued interest$348 $365 
Current maturities of securitized long-term debt$8,418 $8,207 
Securitized long-term debt$72,609 $76,871 
The following table summarizes the impact of AEK on our condensed consolidated statements of comprehensive income, for the period indicated:
Three Months Ended March 31Six Months Ended March 31
2025202420252024
 (In thousands)
Operating revenues$2,951 $3,469 $6,344 $6,802 
Operation and maintenance expense(216)(224)(277)(224)
Amortization expense(1,689)(2,103)(3,953)(4,269)
Interest expense, net(1,046)(1,142)(2,114)(2,309)
Income before income taxes$— $— $— $— $— 
The securitized long-term debt is recorded at carrying value. The fair value of the securitized long-term debt is determined using third party market value quotations, which are considered Level 2 fair value measurements for debt instruments where fair value is determined using the most recent available quoted market price. The carrying value and fair value of the securitized long-term debt as of March 31, 2025 was $81.0 million and $81.9 million, and as of September 30, 2024 was $85.1 million and $87.8 million.
Texas
In March 2023, the Texas Natural Gas Securitization Finance Corporation (the Finance Corporation), with the authority of the Texas Public Finance Authority (TPFA), issued $3.5 billion in customer rate relief bonds with varying scheduled final maturities from 12 to 18 years. The bonds are obligations of the Finance Corporation, payable from the customer rate relief charges and other bond collateral, and are not an obligation of Atmos Energy. We began collecting the customer rate relief charges on October 1, 2023, and any such property collected is solely owned by the Finance Corporation and not available to pay creditors of Atmos Energy.
v3.25.1
Interim Pension and Other Postretirement Benefit Plan Information
 6 Months Ended
Mar. 31, 2025
Retirement Benefits, Description [Abstract]  
Interim Pension and Other Postretirement Benefit Plan Information Interim Pension and Other Postretirement Benefit Plan Information
The components of our net periodic pension cost for our pension and other postretirement benefit plans for the three and six months ended March 31, 2025 and 2024 are presented in the following tables. Most of these costs are recoverable through our tariff rates. A portion of these costs is capitalized into our rate base or deferred as a regulatory asset or liability. The remaining costs are recorded as a component of operation and maintenance expense or other non-operating expense.
 Three Months Ended March 31
 Pension BenefitsOther Benefits
 2025202420252024
 (In thousands)
Components of net periodic pension cost:
Service cost$2,837 $2,405 $2,033 $1,507 
Interest cost (1)
6,663 7,430 3,365 3,509 
Expected return on assets (1)
(7,655)(7,202)(3,831)(3,128)
Amortization of prior service cost (credit) (1)
— — (3,260)(3,260)
Amortization of actuarial (gain) loss (1)
256 97 (2,429)(2,718)
Net periodic pension cost$2,101 $2,730 $(4,122)$(4,090)
 Six Months Ended March 31
 Pension BenefitsOther Benefits
2025202420252024
 (In thousands)
Components of net periodic pension cost:
Service cost$5,674 $4,794 $4,066 $3,014 
Interest cost (1)
13,326 14,926 6,731 7,017 
Expected return on assets (1)
(15,309)(14,404)(7,663)(6,256)
Amortization of prior service cost (credit) (1)
— — (6,520)(6,520)
Amortization of actuarial (gain) loss (1)
511 215 (4,858)(5,436)
Settlements (1)
— 776 — — 
Net periodic pension cost$4,202 $6,307 $(8,244)$(8,181)
(1)    The components of net periodic cost other than the service cost component are included in the line item other non-operating expense in the condensed consolidated statements of comprehensive income or are capitalized on the condensed consolidated balance sheets as a regulatory asset or liability, as described in Note 2 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024.
v3.25.1
Commitments and Contingencies
 6 Months Ended
Mar. 31, 2025
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies Commitments and Contingencies
Litigation and Environmental Matters
In the normal course of business, we are subject to various legal and regulatory proceedings. For such matters, we record liabilities when they are considered probable and estimable, based on currently available facts, our historical experience and our estimates of the ultimate outcome or resolution of the liability in the future. While the outcome of these proceedings is uncertain and a loss in excess of the amount we have accrued is possible though not reasonably estimable, it is the opinion of management that any amounts exceeding the accruals will not have a material adverse impact on our financial position, results of operations or cash flows.
The National Transportation Safety Board (NTSB) issued a Preliminary Report on February 14, 2024 relating to its investigation of two incidents that occurred in Jackson, Mississippi on January 24 and 27, 2024 that resulted in one fatality. Atmos Energy is working closely with the NTSB and other state and federal regulators to help determine causal factors.
The NTSB issued a Preliminary Report on December 30, 2024 relating to its investigation of an incident that occurred in Avondale, Louisiana on December 2, 2024 that resulted in one fatality. Atmos Energy is working closely with the NTSB and other state and federal regulators to help determine causal factors.
We are a party to various other litigation and environmental-related matters or claims that have arisen in the ordinary course of our business. While the results of such litigation and response actions to such environmental-related matters or claims cannot be predicted with certainty, we continue to believe the final outcome of such litigation and matters or claims will not have a material adverse effect on our financial condition, results of operations, or cash flows.
Purchase Commitments
Our distribution divisions maintain supply contracts with several vendors that generally cover a period of up to one year. Commitments for estimated base gas volumes are established under these contracts on a monthly basis at contractually negotiated prices. Commitments for incremental daily purchases are made as necessary during the month in accordance with the terms of the individual contract.
Our Mid-Tex Division also maintains a limited number of long-term supply contracts to ensure a reliable source of gas for our customers in its service area, which obligate it to purchase specified volumes at prices under contracts indexed to natural gas hubs or fixed price contracts. These purchase commitment contracts are detailed in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024. At March 31, 2025, we were committed to purchase 67.5 Bcf within one year and 57.5 Bcf within two to three years under indexed contracts. At March 31, 2025, we had no commitments under fixed price contracts.
Rate Regulatory Proceedings
As of March 31, 2025, routine rate regulatory proceedings were in progress in several of our service areas, which are discussed in further detail below in Management’s Discussion and Analysis — Recent Ratemaking Developments. Except for these proceedings, there were no material changes to rate regulatory proceedings for the six months ended March 31, 2025.
v3.25.1
Income Taxes
 6 Months Ended
Mar. 31, 2025
Income Tax Disclosure [Abstract]  
Income Taxes Income Taxes
Income Tax Expense
Our interim effective tax rates reflect the estimated annual effective tax rates for the fiscal years ended September 30, 2025 and 2024, adjusted for tax expense associated with certain discrete items. The effective tax rates for the three months ended March 31, 2025 and 2024 were 19.5% and 15.7% and for the six months ended March 31, 2025 and 2024 were 19.0% and 15.3%. These effective tax rates differ from the federal statutory tax rate of 21% primarily due to the amortization of excess deferred federal income tax liabilities, tax credits, state income taxes, and other permanent book-to-tax differences. These adjustments have a relative impact on the effective tax rate proportionally to pretax income or loss.
Regulatory Excess Deferred Taxes
Regulatory excess net deferred taxes represent changes in our net deferred tax liability related to our cost of service ratemaking due to the enactment of the Tax Cuts and Jobs Act of 2017 (the TCJA), a Kansas legislative change enacted in fiscal 2020, and a Louisiana legislative change enacted in fiscal 2025. Currently, the regulatory excess net deferred tax liability of $178.6 million is being returned over various periods. Of this amount, $115.5 million is being returned to customers over 12 - 60 months. An additional $48.6 million is being returned to customers on a provisional basis over 15 - 68 years until our regulators establish the final refund periods. The refund of the remaining $14.5 million will be addressed in future rate proceedings.
As of March 31, 2025 and September 30, 2024, $73.9 million and $79.7 million is recorded in other current liabilities.
v3.25.1
Financial Instruments
 6 Months Ended
Mar. 31, 2025
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Financial Instruments Financial Instruments
We currently use financial instruments to mitigate commodity price risk and interest rate risk. The objectives and strategies for using financial instruments and the related accounting for these financial instruments are fully described in Notes 2 and 16 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024. During the six months ended March 31, 2025, there were no material changes in our objectives, strategies, and accounting for using financial instruments. Our financial instruments do not contain any credit-risk-related or other contingent features that could cause payments to be accelerated when our financial instruments are in net liability positions. The following summarizes those objectives and strategies.
Commodity Risk Management Activities
Our purchased gas cost adjustment mechanisms essentially insulate our distribution segment from commodity price risk; however, our customers are exposed to the effects of volatile natural gas prices. We manage this exposure through a combination of physical storage, fixed-price forward contracts, and financial instruments, primarily over-the-counter swap and option contracts, in an effort to minimize the impact of natural gas price volatility on our customers during the winter heating season.
We typically seek to hedge between 25 and 50 percent of anticipated heating season gas purchases using financial instruments. For the 2024-2025 heating season (generally October through March), in the jurisdictions where we are permitted to utilize financial instruments, we hedged approximately 24.0 Bcf of the winter flowing gas requirements. We have not designated these financial instruments as hedges for accounting purposes.
Interest Rate Risk Management Activities
We manage interest rate risk by periodically entering into financial instruments to effectively fix the Treasury yield component of the interest cost associated with anticipated financings.
The following table summarizes our existing forward starting interest rate swaps as of March 31, 2025. These swaps were designated as cash flow hedges at the time the agreements were executed.
Planned Debt Issuance DateAmount Hedged
(In thousands)
Fiscal 2026$300,000 
$300,000 
Quantitative Disclosures Related to Financial Instruments
The following tables present detailed information concerning the impact of financial instruments on our condensed consolidated balance sheet and statements of comprehensive income.
As of March 31, 2025, our financial instruments were comprised of both long and short commodity positions. A long position is a contract to purchase the commodity, while a short position is a contract to sell the commodity. As of March 31, 2025, we had 4,017 MMcf of net long commodity contracts outstanding. These contracts have not been designated as hedges.
Financial Instruments on the Balance Sheet
The following tables present the fair value and balance sheet classification of our financial instruments as of March 31, 2025 and September 30, 2024. The gross amounts of recognized assets and liabilities are netted within our condensed consolidated balance sheets to the extent that we have netting arrangements with our counterparties. However, as of March 31, 2025 and September 30, 2024, no gross amounts and no cash collateral were netted within our consolidated balance sheet.
March 31, 2025
Balance Sheet LocationAssetsLiabilities
   (In thousands)
Designated As Hedges:
Interest rate contractsOther current assets /
Other current liabilities		$114,996 $— 
Total114,996 — 
Not Designated As Hedges:
Commodity contractsOther current assets /
Other current liabilities		8,213 (561)
Total8,213 (561)
Gross / Net Financial Instruments$123,209 $(561)
 
September 30, 2024
Balance Sheet LocationAssetsLiabilities
   (In thousands)
Designated As Hedges:
Interest rate contractsDeferred charges and other assets /
Deferred credits and other liabilities		$91,981 $— 
Total91,981 — 
Not Designated As Hedges:
Commodity contractsOther current assets /
Other current liabilities		2,091 (7,324)
Commodity contractsDeferred charges and other assets /
Deferred credits and other liabilities		2,216 (313)
Total4,307 (7,637)
Gross / Net Financial Instruments$96,288 $(7,637)
Impact of Financial Instruments on the Statement of Comprehensive Income
Cash Flow Hedges
As discussed above, our distribution segment has interest rate agreements, which we designated as cash flow hedges at the time the agreements were executed. The net (gain) loss on settled interest rate agreements reclassified from AOCI into interest charges on our condensed consolidated statements of comprehensive income for the three months ended March 31, 2025 and 2024 was $(5.1) million and $(3.2) million and for the six months ended March 31, 2025 and 2024 was $(10.2) million and $(6.4) million.
The following table summarizes the gains and losses arising from hedging transactions that were recognized as a component of other comprehensive income (loss), net of taxes, for the three and six months ended March 31, 2025 and 2024.
 Three Months Ended March 31Six Months Ended March 31
 2025202420252024
 (In thousands)
Increase (decrease) in fair value:
Interest rate agreements$(1,678)$29,650 $18,041 $(18,091)
Recognition of (gains) losses in earnings due to settlements:
Interest rate agreements(3,982)(2,492)(7,140)(4,983)
Total other comprehensive income (loss) from hedging, net of tax$(5,660)$27,158 $10,901 $(23,074)
Deferred gains (losses) recorded in AOCI associated with our interest rate agreements are recognized in earnings as they are amortized over the terms of the underlying debt instruments. As of March 31, 2025, we had $387.0 million of net realized gains in AOCI associated with our interest rate agreements. The following amounts, net of deferred taxes, represent the expected recognition in earnings of the deferred net gains recorded in AOCI associated with our interest rate agreements, based upon the fair values of these agreements at the date of settlement. The remaining amortization periods for these settled amounts extend through fiscal 2055. However, the table below does not include the expected recognition in earnings of our outstanding interest rate swaps as those instruments have not yet settled.
Interest Rate
Agreements
 (In thousands)
Next twelve months$15,925 
Thereafter371,080 
Total$387,005 

Financial Instruments Not Designated as Hedges
As discussed above, commodity contracts which are used in our distribution segment are not designated as hedges. However, there is no earnings impact on our distribution segment as a result of the use of these financial instruments because the gains and losses arising from the use of these financial instruments are recognized in the consolidated statement of comprehensive income as a component of purchased gas cost when the related costs are recovered through our rates and recognized in revenue. Accordingly, the impact of these financial instruments is excluded from this presentation.
v3.25.1
Fair Value Measurements
 6 Months Ended
Mar. 31, 2025
Fair Value Disclosures [Abstract]  
Fair Value Measurements Fair Value Measurements
We report certain assets and liabilities at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). We record cash and cash equivalents, restricted cash and cash equivalents, accounts receivable, accounts payable, and short-term debt at carrying value, which substantially approximates fair value due to the short-term nature of these assets and liabilities. For other financial assets and liabilities, we primarily use quoted market prices and other observable market pricing information to minimize the use of unobservable pricing inputs in our measurements when determining fair value. The methods used to determine fair value for our assets and liabilities are fully described in Note 2 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024. During the six months ended March 31, 2025, there were no changes in these methods.
Fair value measurements also apply to the valuation of our pension and postretirement plan assets. Current accounting guidance requires employers to annually disclose information about fair value measurements of the assets of a defined benefit pension or other postretirement plan. The fair value of these assets is presented in Note 11 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024.
Quantitative Disclosures
Financial Instruments
The classification of our fair value measurements requires judgment regarding the degree to which market data is observable or corroborated by observable market data. Authoritative accounting literature establishes a fair value hierarchy that prioritizes the inputs used to measure fair value based on observable and unobservable data. The hierarchy categorizes the inputs into three levels, with the highest priority given to unadjusted quoted prices in active markets for identical assets and liabilities (Level 1), with the lowest priority given to unobservable inputs (Level 3). The following tables summarize, by level within the fair value hierarchy, our assets and liabilities that were accounted for at fair value on a recurring basis as of March 31, 2025 and September 30, 2024. Assets and liabilities are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement.
Quoted
Prices in
Active
Markets
(Level 1)
Significant
Other
Observable
Inputs
(Level 2)(1)
Significant
Other
Unobservable
Inputs
(Level 3)		Netting and
Cash
Collateral		March 31, 2025
 (In thousands)
Assets:
Financial instruments$— $123,209 $— $— $123,209 
Debt and equity securities
Registered investment companies27,787 — — — 27,787 
Bond mutual funds40,955 — — — 40,955 
Bonds (2)
— 37,118 — — 37,118 
Money market funds— 3,189 — — 3,189 
Total debt and equity securities68,742 40,307 — — 109,049 
Total assets$68,742 $163,516 $— $— $232,258 
Liabilities:
Financial instruments$— $561 $— $— $561 

Quoted
Prices in
Active
Markets
(Level 1)
Significant
Other
Observable
Inputs
(Level 2)(1)
Significant
Other
Unobservable
Inputs
(Level 3)		Netting and
Cash
Collateral		September 30, 2024
 (In thousands)
Assets:
Financial instruments$— $96,288 $— $— $96,288 
Debt and equity securities
Registered investment companies28,311 — — — 28,311 
Bond mutual funds40,341 — — — 40,341 
Bonds (2)
— 39,142 — — 39,142 
Money market funds— 2,800 — — 2,800 
Total debt and equity securities68,652 41,942 — — 110,594 
Total assets$68,652 $138,230 $— $— $206,882 
Liabilities:
Financial instruments$— $7,637 $— $— $7,637 
 
(1)Our Level 2 measurements consist of over-the-counter options and swaps, which are valued using a market-based approach in which observable market prices are adjusted for criteria specific to each instrument, such as the strike price, notional amount or basis differences, municipal and corporate bonds, which are valued based on the most recent available quoted market prices and money market funds that are valued at cost.
(2)Our investments in bonds are considered available-for-sale debt securities in accordance with current accounting guidance.
Debt and equity securities are comprised of our available-for-sale debt securities and our equity securities. As described in Note 2 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024, we evaluate the performance of our available-for-sale debt securities on an investment by investment basis for impairment, taking into consideration the investment’s purpose, volatility, current returns, and any intent to sell the security. As of March 31, 2025, no allowance for credit losses was recorded for our available-for-sale debt securities. At March 31, 2025 and September 30, 2024, the amortized cost of our available-for-sale debt securities was $36.9 million and $38.9 million. At March 31, 2025, we maintained investments in bonds that have contractual maturity dates ranging from April 2025 through January 2028.
Other Fair Value Measures
Our long-term debt is recorded at carrying value. The fair value of our long-term debt, excluding finance leases, is determined using third party market value quotations, which are considered Level 1 fair value measurements for debt instruments with a recent, observable trade or Level 2 fair value measurements for debt instruments where fair value is determined using the most recent available quoted market price. The carrying value of our finance leases materially approximates fair value. The following table presents the carrying value and fair value of our long-term debt, excluding finance leases, debt issuance costs and original issue premium or discount, as of March 31, 2025 and September 30, 2024:
 March 31, 2025September 30, 2024
 (In thousands)
Carrying Amount$8,435,000 $7,785,000 
Fair Value$7,568,621 $7,337,936 
v3.25.1
Concentration of Credit Risk
 6 Months Ended
Mar. 31, 2025
Risks and Uncertainties [Abstract]  
Concentration of Credit Risk Concentration of Credit Risk
Information regarding our concentration of credit risk is disclosed in Note 18 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024. During the six months ended March 31, 2025, there were no material changes in our concentration of credit risk.
v3.25.1
Pay vs Performance Disclosure - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Dec. 31, 2024
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2025
Mar. 31, 2024
Pay vs Performance Disclosure            
Net income $ 485,576 $ 351,858 $ 432,023 $ 311,292 $ 837,434 $ 743,315
v3.25.1
Insider Trading Arrangements
 3 Months Ended
Mar. 31, 2025
shares
Trading Arrangements, by Individual  
Non-Rule 10b5-1 Arrangement Adopted false
Rule 10b5-1 Arrangement Terminated false
Non-Rule 10b5-1 Arrangement Terminated false
Kim R. Cocklin [Member]  
Trading Arrangements, by Individual  
Material Terms of Trading Arrangement
On February 12, 2025, Kim R. Cocklin, Chairman of the Board of Directors of the Company, adopted a Rule 10b5-1 trading arrangement for the sale of 15,000 shares of the Company's common stock, subject to certain conditions. Mr. Cocklin's trading arrangement will terminate on the earlier of (i) December 14, 2025, (ii) the execution of all trades or expiration of all orders relating to such trades under the Rule 10b5-1 trading arrangement, or (iii) such date as the Rule 10b5-1 trading arrangement is otherwise terminated according to its terms.
Name Kim R. Cocklin,
Title Chairman of the Board of Directors
Rule 10b5-1 Arrangement Adopted true
Adoption Date February 12, 2025
Expiration Date December 14, 2025
Arrangement Duration 305 days
Aggregate Available 15,000
v3.25.1
Summary of Significant Accounting Policies (Policies)
 6 Months Ended
Mar. 31, 2025
Accounting Policies [Abstract]  
Recently issued accounting pronouncements
In November 2023, the Financial Accounting Standards Board (FASB) issued guidance which provides updates to qualitative and quantitative reportable segment disclosure requirements, including enhanced disclosures about significant segment expenses and increased interim disclosure requirements, among others. The amendment is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted, and the amendments should be applied retrospectively. This amendment will be effective for our Form 10-K for fiscal 2025 and our Form 10-Q for the first quarter of fiscal 2026. We are currently evaluating the impact this may have on our financial statement disclosures.
In December 2023, the FASB issued guidance which provides qualitative and quantitative updates to the rate reconciliation and income taxes paid disclosures, among others, in order to enhance the transparency of income tax disclosures, including consistent categories and greater disaggregation of information in the rate reconciliation and disaggregation by jurisdiction of income taxes paid. The amendment is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. The amendments should be applied prospectively; however, retrospective application is also permitted. This amendment will be effective for our Form 10-K for fiscal 2026. We are currently evaluating the impact this amendment may have on our financial statement disclosures.
In November 2024, the FASB issued guidance that will require more detailed information about the types of expenses in commonly presented expense captions. The amendment is effective for fiscal years beginning after December 15, 2026, and interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. This amendment will be effective for our Form 10-K for fiscal 2028 and our Form 10-Q for the first quarter of fiscal 2029. We are currently evaluating the impact this may have on our financial statement disclosures.
Earnings per share We use the two-class method of computing earnings per share because we have participating securities in the form of non-vested restricted stock units with a nonforfeitable right to dividend equivalents, for which vesting is predicated solely on the passage of time. The calculation of earnings per share using the two-class method excludes income attributable to these participating securities from the numerator and excludes the dilutive impact of those shares from the denominator. Basic weighted average shares outstanding is calculated based upon the weighted average number of common shares outstanding during the periods presented. Also, this calculation includes fully vested stock awards that have not yet been issued as common stock.
Fair value measurement
We report certain assets and liabilities at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). We record cash and cash equivalents, restricted cash and cash equivalents, accounts receivable, accounts payable, and short-term debt at carrying value, which substantially approximates fair value due to the short-term nature of these assets and liabilities. For other financial assets and liabilities, we primarily use quoted market prices and other observable market pricing information to minimize the use of unobservable pricing inputs in our measurements when determining fair value. The methods used to determine fair value for our assets and liabilities are fully described in Note 2 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024. During the six months ended March 31, 2025, there were no changes in these methods.
v3.25.1
Regulation (Tables)
 6 Months Ended
Mar. 31, 2025
Regulated Operations [Abstract]  
Schedule of Regulatory Assets
Regulatory assets and liabilities as of March 31, 2025 and September 30, 2024 included the following:
March 31,
2025		September 30,
2024
 (In thousands)
Regulatory assets:
Pension and postretirement benefit costs$4,326 $11,243 
Infrastructure mechanisms (1)
239,997 246,734 
Winter Storm Uri incremental costs6,812 10,373 
Deferred gas costs3,830 159,762 
Regulatory excess deferred taxes (2)
50,526 51,380 
Recoverable loss on reacquired debt2,987 3,070 
Deferred pipeline record collection costs39,899 41,742 
APT annual System Safety and Integrity Rider (3)
34,142 38,632 
Other16,270 16,454 
$398,789 $579,390 
Regulatory liabilities:
Regulatory excess deferred taxes (2)
$229,096 $257,001 
Regulatory cost of removal obligation625,899 607,032 
Deferred gas costs54,794 9,142 
APT annual adjustment mechanism78,126 73,119 
Pension and postretirement benefit costs236,382 247,250 
Other51,006 34,338 
$1,275,303 $1,227,882 
 
(1)Infrastructure mechanisms in Texas, Louisiana, and Tennessee allow for the deferral of all eligible expenses associated with capital expenditures incurred pursuant to these rules, including the recording of interest on deferred expenses until the next rate proceeding (rate case or annual rate filing), at which time investment and costs would be recoverable through base rates.
(2)Regulatory excess deferred taxes represent changes in our net deferred tax liability related to our cost of service ratemaking due to the enactment of Tax Cuts and Jobs Act of 2017 (the "TCJA"), a Kansas legislative change enacted in fiscal 2020, and a Louisiana legislative change enacted in fiscal 2025. See Note 12 to the condensed consolidated financial statements for further information.
(3)In APT's general rate case settlement in December 2023, the RRC approved a new annual compliance filing that allows APT to recover certain system safety and integrity costs incurred each year. Costs above a specified benchmark are deferred onto the balance sheet as incurred. Once the filing is approved by the RRC, the revenue and expense are recognized over 12 months resulting in no impact to operating income.
Schedule of Regulatory Liabilities
Regulatory assets and liabilities as of March 31, 2025 and September 30, 2024 included the following:
March 31,
2025		September 30,
2024
 (In thousands)
Regulatory assets:
Pension and postretirement benefit costs$4,326 $11,243 
Infrastructure mechanisms (1)
239,997 246,734 
Winter Storm Uri incremental costs6,812 10,373 
Deferred gas costs3,830 159,762 
Regulatory excess deferred taxes (2)
50,526 51,380 
Recoverable loss on reacquired debt2,987 3,070 
Deferred pipeline record collection costs39,899 41,742 
APT annual System Safety and Integrity Rider (3)
34,142 38,632 
Other16,270 16,454 
$398,789 $579,390 
Regulatory liabilities:
Regulatory excess deferred taxes (2)
$229,096 $257,001 
Regulatory cost of removal obligation625,899 607,032 
Deferred gas costs54,794 9,142 
APT annual adjustment mechanism78,126 73,119 
Pension and postretirement benefit costs236,382 247,250 
Other51,006 34,338 
$1,275,303 $1,227,882 
 
(1)Infrastructure mechanisms in Texas, Louisiana, and Tennessee allow for the deferral of all eligible expenses associated with capital expenditures incurred pursuant to these rules, including the recording of interest on deferred expenses until the next rate proceeding (rate case or annual rate filing), at which time investment and costs would be recoverable through base rates.
(2)Regulatory excess deferred taxes represent changes in our net deferred tax liability related to our cost of service ratemaking due to the enactment of Tax Cuts and Jobs Act of 2017 (the "TCJA"), a Kansas legislative change enacted in fiscal 2020, and a Louisiana legislative change enacted in fiscal 2025. See Note 12 to the condensed consolidated financial statements for further information.
(3)In APT's general rate case settlement in December 2023, the RRC approved a new annual compliance filing that allows APT to recover certain system safety and integrity costs incurred each year. Costs above a specified benchmark are deferred onto the balance sheet as incurred. Once the filing is approved by the RRC, the revenue and expense are recognized over 12 months resulting in no impact to operating income.
v3.25.1
Segment Information (Tables)
 6 Months Ended
Mar. 31, 2025
Segment Reporting [Abstract]  
Schedule of Segment Reporting Information, by Segment
Income statements and capital expenditures for the three and six months ended March 31, 2025 and 2024 by segment are presented in the following tables:
 Three Months Ended March 31, 2025
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Operating revenues from external parties$1,881,742 $68,760 $— $1,950,502 
Intersegment revenues786 190,239 (191,025)— 
Total operating revenues1,882,528 258,999 (191,025)1,950,502 
Purchased gas cost
969,037 968 (190,772)779,233 
Operation and maintenance expense181,887 51,662 (253)233,296 
Depreciation and amortization expense134,546 48,204 — 182,750 
Taxes, other than income113,340 12,944 — 126,284 
Operating income483,718 145,221 — 628,939 
Other non-operating income13,444 10,728 — 24,172 
Interest charges30,087 19,927 — 50,014 
Income before income taxes
467,075 136,022 — 603,097 
Income tax expense86,432 31,089 — 117,521 
Net income$380,643 $104,933 $— $485,576 
Capital expenditures$594,853 $244,813 $— $839,666 
 Three Months Ended March 31, 2024
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Operating revenues from external parties$1,588,394 $58,833 $— $1,647,227 
Intersegment revenues787 164,654 (165,441)— 
Total operating revenues1,589,181 223,487 (165,441)1,647,227 
Purchased gas cost
788,643 840 (165,188)624,295 
Operation and maintenance expense154,956 45,196 (253)199,899 
Depreciation and amortization expense121,384 43,703 — 165,087 
Taxes, other than income98,008 8,948 — 106,956 
Operating income426,190 124,800 — 550,990 
Other non-operating income9,359 7,328 — 16,687 
Interest charges36,784 18,658 — 55,442 
Income before income taxes
398,765 113,470 — 512,235 
Income tax expense56,073 24,139 — 80,212 
Net income$342,692 $89,331 $— $432,023 
Capital expenditures$532,997 $112,879 $— $645,876 
 Six Months Ended March 31, 2025
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Operating revenues from external parties$2,990,311 $136,190 $— $3,126,501 
Intersegment revenues1,552 378,199 (379,751)— 
Total operating revenues2,991,863 514,389 (379,751)3,126,501 
Purchased gas cost
1,391,607 910 (379,236)1,013,281 
Operation and maintenance expense336,401 104,454 (515)440,340 
Depreciation and amortization expense268,173 95,110 — 363,283 
Taxes, other than income195,916 25,262 — 221,178 
Operating income799,766 288,653 — 1,088,419 
Other non-operating income23,528 25,278 — 48,806 
Interest charges64,336 38,603 — 102,939 
Income before income taxes
758,958 275,328 — 1,034,286 
Income tax expense138,102 58,750 — 196,852 
Net income$620,856 $216,578 $— $837,434 
Capital expenditures$1,220,502 $510,355 $— $1,730,857 
 Six Months Ended March 31, 2024
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Operating revenues from external parties$2,693,013 $112,681 $— $2,805,694 
Intersegment revenues1,506 321,975 (323,481)— 
Total operating revenues2,694,519 434,656 (323,481)2,805,694 
Purchased gas cost
1,285,305 844 (322,985)963,164 
Operation and maintenance expense282,571 84,169 (496)366,244 
Depreciation and amortization expense241,069 88,626 — 329,695 
Taxes, other than income178,903 17,593 — 196,496 
Operating income706,671 243,424 — 950,095 
Other non-operating income15,198 19,375 — 34,573 
Interest charges71,365 35,952 — 107,317 
Income before income taxes
650,504 226,847 — 877,351 
Income tax expense86,375 47,661 — 134,036 
Net income$564,129 $179,186 $— $743,315 
Capital expenditures$1,072,155 $343,371 $— $1,415,526 
Balance sheet information at March 31, 2025 and September 30, 2024 by segment is presented in the following tables:
 March 31, 2025
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Net property, plant and equipment$17,422,364 $6,209,859 $— $23,632,223 
Total assets$26,109,156 $6,541,506 $(5,670,281)$26,980,381 
 September 30, 2024
 DistributionPipeline and StorageEliminationsConsolidated
 (In thousands)
Net property, plant and equipment$16,372,659 $5,831,708 $— $22,204,367 
Total assets$24,328,877 $6,181,558 $(5,315,970)$25,194,465 
v3.25.1
Earnings Per Share (Tables)
 6 Months Ended
Mar. 31, 2025
Earnings Per Share [Abstract]  
Schedule of Earnings Per Share, Basic and Diluted
Basic and diluted earnings per share for the three and six months ended March 31, 2025 and 2024 are calculated as follows:
 Three Months Ended March 31Six Months Ended March 31
 2025202420252024
 (In thousands, except per share amounts)
Basic Earnings Per Share
Net income$485,576 $432,023 $837,434 $743,315 
Less: Income allocated to participating securities
245 255 436 442 
Income available to common shareholders
$485,331 $431,768 $836,998 $742,873 
Basic weighted average shares outstanding
159,177 151,271 157,739 150,534 
Net income per share — Basic
$3.05 $2.85 $5.31 $4.93 
Diluted Earnings Per Share
Income available to common shareholders$485,331 $431,768 $836,998 $742,873 
Effect of dilutive shares
— — — — 
Income available to common shareholders
$485,331 $431,768 $836,998 $742,873 
Basic weighted average shares outstanding
159,177 151,271 157,739 150,534 
Dilutive shares1,249 26 1,386 13 
Diluted weighted average shares outstanding
160,426 151,297 159,125 150,547 
Net income per share — Diluted$3.03 $2.85 $5.26 $4.93 
v3.25.1
Revenue and Accounts Receivable (Tables)
 6 Months Ended
Mar. 31, 2025
Revenue from Contract with Customer [Abstract]  
Schedule of Disaggregation of Revenue The following tables disaggregate our revenue from contracts with customers by customer type and segment and provide a reconciliation to total operating revenues, including intersegment revenues, for the three and six months ended March 31, 2025 and 2024.
Three Months Ended March 31, 2025Three Months Ended March 31, 2024
DistributionPipeline and StorageDistributionPipeline and Storage
(In thousands)
Gas sales revenues:
Residential$1,308,691 $— $1,065,296 $— 
Commercial480,108 — 404,701 — 
Industrial38,885 — 30,419 — 
Public authority and other23,921 — 21,120 — 
Total gas sales revenues1,851,605 — 1,521,536 — 
Transportation revenues43,352 266,514 37,607 223,159 
Miscellaneous revenues4,222 4,259 3,724 2,162 
Revenues from contracts with customers1,899,179 270,773 1,562,867 225,321 
Alternative revenue program revenues(20,117)(11,774)22,315 (1,834)
Other revenues3,466 — 3,999 — 
Total operating revenues$1,882,528 $258,999 $1,589,181 $223,487 
Six Months Ended March 31, 2025Six Months Ended March 31, 2024
DistributionPipeline and StorageDistributionPipeline and Storage
(In thousands)
Gas sales revenues:
Residential$2,001,741 $— $1,792,978 $— 
Commercial746,162 — 681,954 — 
Industrial65,206 — 58,650 — 
Public authority and other36,802 — 35,704 — 
Total gas sales revenues2,849,911 — 2,569,286 — 
Transportation revenues80,079 532,543 71,374 438,464 
Miscellaneous revenues7,244 6,923 6,367 5,204 
Revenues from contracts with customers2,937,234 539,466 2,647,027 443,668 
Alternative revenue program revenues47,219 (25,077)39,716 (9,012)
Other revenues7,410 — 7,776 — 
Total operating revenues$2,991,863 $514,389 $2,694,519 $434,656 
Schedule of Allowance for Credit Loss Activity Rollforwards of our allowance for uncollectible accounts for the three and six months ended March 31, 2025 and 2024 are presented in the table below. The allowance excludes the gas cost portion of customers’ bills for approximately 89 percent of our customers as we have the ability to collect these gas costs through our gas cost recovery mechanisms in most of our jurisdictions.
In December 2023, the Mississippi Public Service Commission approved the recovery of uncollectible accounts through our purchased gas cost mechanism over a two-year period rather than through our annual filing mechanism over a one-year period. As a result of this decision, we recorded a $13.9 million reduction to bad debt expense during the first quarter of fiscal 2024. Of this amount, $9.7 million represents future recovery of customer receivables previously written off since April 2022 but not yet recovered through our rates. This amount increased our deferred gas cost regulatory asset. The remaining $4.2 million reduction represents a reversal of our allowance for uncollectible accounts for customer balances that have not yet been written off.
 Three Months Ended March 31, 2025
 (In thousands)
Beginning balance, December 31, 2024$39,166 
Current period provisions14,391 
Write-offs charged against allowance(4,761)
Recoveries of amounts previously written off545 
Ending balance, March 31, 2025
$49,341 
 Three Months Ended March 31, 2024
 (In thousands)
Beginning balance, December 31, 2023$35,406 
Current period provisions12,797 
Write-offs charged against allowance(5,859)
Recoveries of amounts previously written off361 
Ending balance, March 31, 2024
$42,705 
 Six Months Ended March 31, 2025
 (In thousands)
Beginning balance, September 30, 2024
$37,056 
Current period provisions23,015 
Write-offs charged against allowance(12,209)
Recoveries of amounts previously written off1,479 
Ending balance, March 31, 2025
$49,341 
 Six Months Ended March 31, 2024
 (In thousands)
Beginning balance, September 30, 2023
$40,840 
Current period provisions19,547 
Write-offs charged against allowance(14,616)
Recoveries of amounts previously written off1,126 
Mississippi recovery of uncollectible accounts(4,192)
Ending balance, March 31, 2024
$42,705 
v3.25.1
Debt (Tables)
 6 Months Ended
Mar. 31, 2025
Debt Disclosure [Abstract]  
Schedule of Long-term Debt Instruments
Long-term debt at March 31, 2025 and September 30, 2024 consisted of the following:
March 31, 2025September 30, 2024
 (In thousands)
Unsecured 3.00% Senior Notes, due June 2027
$500,000 $500,000 
Unsecured 2.625% Senior Notes, due September 2029
500,000 500,000 
Unsecured 1.50% Senior Notes, due January 2031
600,000 600,000 
Unsecured 5.45% Senior Notes, due October 2032
300,000 300,000 
Unsecured 5.90% Senior Notes, due November 2033

725,000 725,000 
Unsecured 5.95% Senior Notes, due October 2034
200,000 200,000 
Unsecured 5.50% Senior Notes, due June 2041
400,000 400,000 
Unsecured 4.15% Senior Notes, due January 2043
500,000 500,000 
Unsecured 4.125% Senior Notes, due October 2044
750,000 750,000 
Unsecured 4.30% Senior Notes, due October 2048
600,000 600,000 
Unsecured 4.125% Senior Notes, due March 2049
450,000 450,000 
Unsecured 3.375% Senior Notes, due September 2049
500,000 500,000 
Unsecured 2.85% Senior Notes, due February 2052
600,000 600,000 
Unsecured 5.75% Senior Notes, due October 2052
500,000 500,000 
Unsecured 6.20% Senior Notes, due November 2053
500,000 500,000 
Unsecured 5.00% Senior Notes, due December 2054
650,000 — 
Medium-term note Series A, 1995-1, 6.67%, due December 2025
10,000 10,000 
Unsecured 6.75% Debentures, due July 2028
150,000 150,000 
Finance lease obligations48,075 48,890 
Total long-term debt8,483,075 7,833,890 
Less:
Original issue premium on unsecured senior notes and debentures(3,825)(9,071)
Debt issuance cost61,463 57,664 
Current maturities of long-term debt11,712 1,651 
Total long-term debt, net$8,413,725 $7,783,646 
v3.25.1
Shareholders' Equity (Tables)
 6 Months Ended
Mar. 31, 2025
Equity [Abstract]  
Schedule of Reconciliation of Changes in Stockholders Equity
The following tables present a reconciliation of changes in stockholders' equity for the three and six months ended March 31, 2025 and 2024.
 Common stockAdditional
Paid-in
Capital		Accumulated
Other
Comprehensive Income
(Loss)		Retained
Earnings		Total
Number of
Shares		Stated
Value
 (In thousands, except share and per share data)
Balance, September 30, 2024
155,258,845 $776 $7,474,559 $465,715 $4,216,619 $12,157,669 
Net income— — — — 351,858 351,858 
Other comprehensive income— — — 16,423 — 16,423 
Cash dividends ($0.87 per share)
— — — — (135,453)(135,453)
Common stock issued:
Public and other stock offerings3,329,358 17 383,520 — — 383,537 
Stock-based compensation plans137,862 1 6,446 — — 6,447 
Balance, December 31, 2024158,726,065 794 7,864,525 482,138 4,433,024 12,780,481 
Net income— — — — 485,576 485,576 
Other comprehensive loss— — — (5,587)— (5,587)
Cash dividends ($0.87 per share)
— — — — (138,416)(138,416)
Common stock issued:
Public and other stock offerings26,367 — 3,841 — — 3,841 
Stock-based compensation plans82,691 — 12,070 — — 12,070 
Balance, March 31, 2025158,835,123 $794 $7,880,436 $476,551 $4,780,184 $13,137,965 
 Common stockAdditional
Paid-in
Capital		Accumulated
Other
Comprehensive Income
(Loss)		Retained
Earnings		Total
Number of
Shares		Stated
Value
 (In thousands, except share and per share data)
Balance, September 30, 2023
148,492,783 $742 $6,684,120 $518,528 $3,666,674 $10,870,064 
Net income— — — — 311,292 311,292 
Other comprehensive loss— — — (49,936)— (49,936)
Cash dividends ($0.805 per share)
— — — — (119,898)(119,898)
Common stock issued:
Public and other stock offerings2,177,864 11 257,757 — — 257,768 
Stock-based compensation plans163,750 1 3,918 — — 3,919 
Balance, December 31, 2023150,834,397 754 6,945,795 468,592 3,858,068 11,273,209 
Net income— — — — 432,023 432,023 
Other comprehensive income— — — 27,108 — 27,108 
Cash dividends ($0.805 per share)
— — — — (121,667)(121,667)
Common stock issued:
Public and other stock offerings34,687 — 4,025 — — 4,025 
Stock-based compensation plans5,468 — 3,941 — — 3,941 
Balance, March 31, 2024150,874,552 $754 $6,953,761 $495,700 $4,168,424 $11,618,639 
Schedule of Forward Sales Agreements Additionally, we had $1.7 billion in available proceeds from outstanding forward sale agreements, as detailed below.
MaturityShares AvailableNet Proceeds Available
(In thousands)		Forward Price
June 30, 2025630,514 $73,406 $116.42 
September 30, 2025815,655 96,313 $118.08 
December 31, 20252,344,567 297,650 $126.95 
March 31, 20263,627,033 463,284 $127.73 
June 30, 2026669,043 89,150 $133.25 
December 31, 20263,392,352 472,749 $139.36 
March 31, 20271,119,095 $167,073 $149.29 
Total12,598,259 $1,659,625 $131.73 
Schedule of Accumulated Other Comprehensive Income (Loss) The following tables provide the components of our accumulated other comprehensive income (loss) balances, net of the related tax effects allocated to each component of other comprehensive income (loss).
Available-
for-Sale
Securities		Interest Rate
Agreement
Cash Flow
Hedges		Total
 (In thousands)
September 30, 2024$213 $465,502 $465,715 
Other comprehensive income (loss) before reclassifications(65)18,041 17,976 
Amounts reclassified from accumulated other comprehensive income— (7,140)(7,140)
Net current-period other comprehensive income (loss)(65)10,901 10,836 
March 31, 2025$148 $476,403 $476,551 
 
Available-
for-Sale
Securities		Interest Rate
Agreement
Cash Flow
Hedges		Total
 (In thousands)
September 30, 2023$(369)$518,897 $518,528 
Other comprehensive income (loss) before reclassifications246 (18,091)(17,845)
Amounts reclassified from accumulated other comprehensive income— (4,983)(4,983)
Net current-period other comprehensive income (loss)246 (23,074)(22,828)
March 31, 2024$(123)$495,823 $495,700 
v3.25.1
Securitization (Tables)
 6 Months Ended
Mar. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Schedule of Condensed Consolidated Balance Sheet
The following table summarizes the impact of AEK on our condensed consolidated balance sheets, for the periods indicated:
March 31, 2025September 30, 2024
 (In thousands)
Restricted cash and cash equivalents$1,616 $1,516 
Other current assets$3 $3 
Securitized intangible asset, net$78,892 $82,844 
Accrued interest$348 $365 
Current maturities of securitized long-term debt$8,418 $8,207 
Securitized long-term debt$72,609 $76,871 
Schedule of Condensed Consolidated Statements of Comprehensive Income
The following table summarizes the impact of AEK on our condensed consolidated statements of comprehensive income, for the period indicated:
Three Months Ended March 31Six Months Ended March 31
2025202420252024
 (In thousands)
Operating revenues$2,951 $3,469 $6,344 $6,802 
Operation and maintenance expense(216)(224)(277)(224)
Amortization expense(1,689)(2,103)(3,953)(4,269)
Interest expense, net(1,046)(1,142)(2,114)(2,309)
Income before income taxes$— $— $— $— $— 
v3.25.1
Interim Pension and Other Postretirement Benefit Plan Information (Tables)
 6 Months Ended
Mar. 31, 2025
Retirement Benefits, Description [Abstract]  
Schedule of Net Benefit Costs
 Three Months Ended March 31
 Pension BenefitsOther Benefits
 2025202420252024
 (In thousands)
Components of net periodic pension cost:
Service cost$2,837 $2,405 $2,033 $1,507 
Interest cost (1)
6,663 7,430 3,365 3,509 
Expected return on assets (1)
(7,655)(7,202)(3,831)(3,128)
Amortization of prior service cost (credit) (1)
— — (3,260)(3,260)
Amortization of actuarial (gain) loss (1)
256 97 (2,429)(2,718)
Net periodic pension cost$2,101 $2,730 $(4,122)$(4,090)
 Six Months Ended March 31
 Pension BenefitsOther Benefits
2025202420252024
 (In thousands)
Components of net periodic pension cost:
Service cost$5,674 $4,794 $4,066 $3,014 
Interest cost (1)
13,326 14,926 6,731 7,017 
Expected return on assets (1)
(15,309)(14,404)(7,663)(6,256)
Amortization of prior service cost (credit) (1)
— — (6,520)(6,520)
Amortization of actuarial (gain) loss (1)
511 215 (4,858)(5,436)
Settlements (1)
— 776 — — 
Net periodic pension cost$4,202 $6,307 $(8,244)$(8,181)
(1)    The components of net periodic cost other than the service cost component are included in the line item other non-operating expense in the condensed consolidated statements of comprehensive income or are capitalized on the condensed consolidated balance sheets as a regulatory asset or liability, as described in Note 2 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2024.
v3.25.1
Financial Instruments (Tables)
 6 Months Ended
Mar. 31, 2025
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Schedule of Interest Rate Derivatives
The following table summarizes our existing forward starting interest rate swaps as of March 31, 2025. These swaps were designated as cash flow hedges at the time the agreements were executed.
Planned Debt Issuance DateAmount Hedged
(In thousands)
Fiscal 2026$300,000 
$300,000 
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value
The following tables present the fair value and balance sheet classification of our financial instruments as of March 31, 2025 and September 30, 2024. The gross amounts of recognized assets and liabilities are netted within our condensed consolidated balance sheets to the extent that we have netting arrangements with our counterparties. However, as of March 31, 2025 and September 30, 2024, no gross amounts and no cash collateral were netted within our consolidated balance sheet.
March 31, 2025
Balance Sheet LocationAssetsLiabilities
   (In thousands)
Designated As Hedges:
Interest rate contractsOther current assets /
Other current liabilities		$114,996 $— 
Total114,996 — 
Not Designated As Hedges:
Commodity contractsOther current assets /
Other current liabilities		8,213 (561)
Total8,213 (561)
Gross / Net Financial Instruments$123,209 $(561)
 
September 30, 2024
Balance Sheet LocationAssetsLiabilities
   (In thousands)
Designated As Hedges:
Interest rate contractsDeferred charges and other assets /
Deferred credits and other liabilities		$91,981 $— 
Total91,981 — 
Not Designated As Hedges:
Commodity contractsOther current assets /
Other current liabilities		2,091 (7,324)
Commodity contractsDeferred charges and other assets /
Deferred credits and other liabilities		2,216 (313)
Total4,307 (7,637)
Gross / Net Financial Instruments$96,288 $(7,637)
Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss)
The following table summarizes the gains and losses arising from hedging transactions that were recognized as a component of other comprehensive income (loss), net of taxes, for the three and six months ended March 31, 2025 and 2024.
 Three Months Ended March 31Six Months Ended March 31
 2025202420252024
 (In thousands)
Increase (decrease) in fair value:
Interest rate agreements$(1,678)$29,650 $18,041 $(18,091)
Recognition of (gains) losses in earnings due to settlements:
Interest rate agreements(3,982)(2,492)(7,140)(4,983)
Total other comprehensive income (loss) from hedging, net of tax$(5,660)$27,158 $10,901 $(23,074)
Schedule of Expected Deferred Gains (Losses) Recognition The following amounts, net of deferred taxes, represent the expected recognition in earnings of the deferred net gains recorded in AOCI associated with our interest rate agreements, based upon the fair values of these agreements at the date of settlement. The remaining amortization periods for these settled amounts extend through fiscal 2055. However, the table below does not include the expected recognition in earnings of our outstanding interest rate swaps as those instruments have not yet settled.
Interest Rate
Agreements
 (In thousands)
Next twelve months$15,925 
Thereafter371,080 
Total$387,005 
v3.25.1
Fair Value Measurements (Tables)
 6 Months Ended
Mar. 31, 2025
Fair Value Disclosures [Abstract]  
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis The following tables summarize, by level within the fair value hierarchy, our assets and liabilities that were accounted for at fair value on a recurring basis as of March 31, 2025 and September 30, 2024. Assets and liabilities are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement.
Quoted
Prices in
Active
Markets
(Level 1)
Significant
Other
Observable
Inputs
(Level 2)(1)
Significant
Other
Unobservable
Inputs
(Level 3)		Netting and
Cash
Collateral		March 31, 2025
 (In thousands)
Assets:
Financial instruments$— $123,209 $— $— $123,209 
Debt and equity securities
Registered investment companies27,787 — — — 27,787 
Bond mutual funds40,955 — — — 40,955 
Bonds (2)
— 37,118 — — 37,118 
Money market funds— 3,189 — — 3,189 
Total debt and equity securities68,742 40,307 — — 109,049 
Total assets$68,742 $163,516 $— $— $232,258 
Liabilities:
Financial instruments$— $561 $— $— $561 

Quoted
Prices in
Active
Markets
(Level 1)
Significant
Other
Observable
Inputs
(Level 2)(1)
Significant
Other
Unobservable
Inputs
(Level 3)		Netting and
Cash
Collateral		September 30, 2024
 (In thousands)
Assets:
Financial instruments$— $96,288 $— $— $96,288 
Debt and equity securities
Registered investment companies28,311 — — — 28,311 
Bond mutual funds40,341 — — — 40,341 
Bonds (2)
— 39,142 — — 39,142 
Money market funds— 2,800 — — 2,800 
Total debt and equity securities68,652 41,942 — — 110,594 
Total assets$68,652 $138,230 $— $— $206,882 
Liabilities:
Financial instruments$— $7,637 $— $— $7,637 
 
(1)Our Level 2 measurements consist of over-the-counter options and swaps, which are valued using a market-based approach in which observable market prices are adjusted for criteria specific to each instrument, such as the strike price, notional amount or basis differences, municipal and corporate bonds, which are valued based on the most recent available quoted market prices and money market funds that are valued at cost.
(2)Our investments in bonds are considered available-for-sale debt securities in accordance with current accounting guidance.
Schedule of Carrying Values and Estimated Fair Values of Long-term Debt The following table presents the carrying value and fair value of our long-term debt, excluding finance leases, debt issuance costs and original issue premium or discount, as of March 31, 2025 and September 30, 2024:
 March 31, 2025September 30, 2024
 (In thousands)
Carrying Amount$8,435,000 $7,785,000 
Fair Value$7,568,621 $7,337,936 
v3.25.1
Nature of Business (Details)
customer in Millions
Mar. 31, 2025
state
customer
regulated_distribution_division
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Number of customers serviced (over) | customer 3.3
Number of regulated distribution divisions | regulated_distribution_division 6
Number of states with service areas | state 8
v3.25.1
Summary of Significant Accounting Policies (Details)
 3 Months Ended
Mar. 31, 2025
USD ($)
Accounting Policies [Abstract]  
Impairment loss for goodwill $ 0
v3.25.1
Regulation - Schedule of Regulatory Assets and Liabilities (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Sep. 30, 2024
Regulatory Asset [Line Items]    
Regulatory assets $ 398,789 $ 579,390
Regulatory Liabilities [Line Items]    
Regulatory liabilities 1,275,303 1,227,882
Regulatory excess deferred taxes    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 229,096 257,001
Regulatory cost of removal obligation    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 625,899 607,032
Deferred gas costs    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 54,794 9,142
APT annual adjustment mechanism    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 78,126 73,119
Pension and postretirement benefit costs    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 236,382 247,250
Other    
Regulatory Liabilities [Line Items]    
Regulatory liabilities 51,006 34,338
Pension and postretirement benefit costs    
Regulatory Asset [Line Items]    
Regulatory assets 4,326 11,243
Infrastructure mechanisms    
Regulatory Asset [Line Items]    
Regulatory assets 239,997 246,734
Winter Storm Uri incremental costs    
Regulatory Asset [Line Items]    
Regulatory assets 6,812 10,373
Deferred gas costs    
Regulatory Asset [Line Items]    
Regulatory assets 3,830 159,762
Regulatory excess deferred taxes    
Regulatory Asset [Line Items]    
Regulatory assets 50,526 51,380
Recoverable loss on reacquired debt    
Regulatory Asset [Line Items]    
Regulatory assets 2,987 3,070
Deferred pipeline record collection costs    
Regulatory Asset [Line Items]    
Regulatory assets 39,899 41,742
APT annual System Safety and Integrity Rider    
Regulatory Asset [Line Items]    
Regulatory assets $ 34,142 38,632
Regulatory asset, recognition period 12 months  
Other    
Regulatory Asset [Line Items]    
Regulatory assets $ 16,270 $ 16,454
v3.25.1
Regulation - Narrative (Details) - Texas - Winter Storm Uri incremental costs - Winter Storm Uri - USD ($)
$ in Millions
 6 Months Ended 12 Months Ended 31 Months Ended
Mar. 31, 2025
Sep. 30, 2024
Mar. 31, 2025
Regulatory Asset [Line Items]      
Regulatory asset, deferred costs     $ 32.4
Regulatory asset, recovered cost $ 3.6 $ 22.0  
Regulatory asset, deferred costs, remaining 6.8   6.8
Other current assets      
Regulatory Asset [Line Items]      
Regulatory asset, deferred costs, remaining 0.4   0.4
Deferred charges and other assets      
Regulatory Asset [Line Items]      
Regulatory asset, deferred costs, remaining $ 6.4   $ 6.4
v3.25.1
Segment Information - Narrative (Details)
Mar. 31, 2025
state
Segment Reporting [Abstract]  
Number of states with service areas 8
v3.25.1
Segment Information - Schedule of Income Statements and Capital Expenditures By Segment (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Dec. 31, 2024
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2025
Mar. 31, 2024
Segment Reporting Information [Line Items]            
Operating revenues $ 1,950,502   $ 1,647,227   $ 3,126,501 $ 2,805,694
Purchased gas cost 779,233   624,295   1,013,281 963,164
Operation and maintenance expense 233,296   199,899   440,340 366,244
Depreciation and amortization expense 182,750   165,087   363,283 329,695
Taxes, other than income 126,284   106,956   221,178 196,496
Operating income 628,939   550,990   1,088,419 950,095
Other non-operating income (expense) 24,172   16,687   48,806 34,573
Interest charges 50,014   55,442   102,939 107,317
Income before income taxes 603,097   512,235   1,034,286 877,351
Income tax expense 117,521   80,212   196,852 134,036
Net income 485,576 $ 351,858 432,023 $ 311,292 837,434 743,315
Capital expenditures 839,666   645,876   1,730,857 1,415,526
Distribution            
Segment Reporting Information [Line Items]            
Operating revenues 1,881,742   1,588,394   2,990,311 2,693,013
Pipeline and Storage            
Segment Reporting Information [Line Items]            
Operating revenues 68,760   58,833   136,190 112,681
Operating Segments | Distribution            
Segment Reporting Information [Line Items]            
Operating revenues 1,882,528   1,589,181   2,991,863 2,694,519
Purchased gas cost 969,037   788,643   1,391,607 1,285,305
Operation and maintenance expense 181,887   154,956   336,401 282,571
Depreciation and amortization expense 134,546   121,384   268,173 241,069
Taxes, other than income 113,340   98,008   195,916 178,903
Operating income 483,718   426,190   799,766 706,671
Other non-operating income (expense) 13,444   9,359   23,528 15,198
Interest charges 30,087   36,784   64,336 71,365
Income before income taxes 467,075   398,765   758,958 650,504
Income tax expense 86,432   56,073   138,102 86,375
Net income 380,643   342,692   620,856 564,129
Capital expenditures 594,853   532,997   1,220,502 1,072,155
Operating Segments | Pipeline and Storage            
Segment Reporting Information [Line Items]            
Operating revenues 258,999   223,487   514,389 434,656
Purchased gas cost 968   840   910 844
Operation and maintenance expense 51,662   45,196   104,454 84,169
Depreciation and amortization expense 48,204   43,703   95,110 88,626
Taxes, other than income 12,944   8,948   25,262 17,593
Operating income 145,221   124,800   288,653 243,424
Other non-operating income (expense) 10,728   7,328   25,278 19,375
Interest charges 19,927   18,658   38,603 35,952
Income before income taxes 136,022   113,470   275,328 226,847
Income tax expense 31,089   24,139   58,750 47,661
Net income 104,933   89,331   216,578 179,186
Capital expenditures 244,813   112,879   510,355 343,371
Eliminations            
Segment Reporting Information [Line Items]            
Operating revenues (191,025)   (165,441)   (379,751) (323,481)
Purchased gas cost (190,772)   (165,188)   (379,236) (322,985)
Operation and maintenance expense (253)   (253)   (515) (496)
Depreciation and amortization expense 0   0   0 0
Taxes, other than income 0   0   0 0
Operating income 0   0   0 0
Other non-operating income (expense) 0   0   0 0
Interest charges 0   0   0 0
Income before income taxes 0   0   0 0
Income tax expense 0   0   0 0
Net income 0   0   0 0
Capital expenditures 0   0   0 0
Eliminations | Distribution            
Segment Reporting Information [Line Items]            
Operating revenues (786)   (787)   (1,552) (1,506)
Eliminations | Pipeline and Storage            
Segment Reporting Information [Line Items]            
Operating revenues $ (190,239)   $ (164,654)   $ (378,199) $ (321,975)
v3.25.1
Segment Information - Schedule of Balance Sheet Information by Segment (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Sep. 30, 2024
Segment Reporting Information [Line Items]    
Net property, plant and equipment $ 23,632,223 $ 22,204,367
Total assets 26,980,381 25,194,465
Operating Segments | Distribution    
Segment Reporting Information [Line Items]    
Net property, plant and equipment 17,422,364 16,372,659
Total assets 26,109,156 24,328,877
Operating Segments | Pipeline and Storage    
Segment Reporting Information [Line Items]    
Net property, plant and equipment 6,209,859 5,831,708
Total assets 6,541,506 6,181,558
Eliminations    
Segment Reporting Information [Line Items]    
Net property, plant and equipment 0 0
Total assets $ (5,670,281) $ (5,315,970)
v3.25.1
Earnings Per Share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Dec. 31, 2024
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2025
Mar. 31, 2024
Basic Earnings Per Share            
Net income $ 485,576 $ 351,858 $ 432,023 $ 311,292 $ 837,434 $ 743,315
Less: Income allocated to participating securities 245   255   436 442
Income available to common shareholders $ 485,331   $ 431,768   $ 836,998 $ 742,873
Basic weighted average shares outstanding (in shares) 159,177   151,271   157,739 150,534
Net income per share - Basic (USD per share) $ 3.05   $ 2.85   $ 5.31 $ 4.93
Diluted Earnings Per Share            
Income available to common shareholders $ 485,331   $ 431,768   $ 836,998 $ 742,873
Effect of dilutive shares 0   0   0 0
Income available to common shareholders $ 485,331   $ 431,768   $ 836,998 $ 742,873
Basic weighted average shares outstanding (in shares) 159,177   151,271   157,739 150,534
Dilutive shares (in shares) 1,249   26   1,386 13
Diluted weighted average shares outstanding (in shares) 160,426   151,297   159,125 150,547
Net income per share - Diluted (USD per share) $ 3.03   $ 2.85   $ 5.26 $ 4.93
v3.25.1
Revenue and Accounts Receivable - Schedule of Disaggregation of Revenue (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Disaggregation of Revenue [Line Items]        
Total operating revenues $ 1,950,502 $ 1,647,227 $ 3,126,501 $ 2,805,694
Distribution        
Disaggregation of Revenue [Line Items]        
Total operating revenues 1,881,742 1,588,394 2,990,311 2,693,013
Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Total operating revenues 68,760 58,833 136,190 112,681
Operating Segments | Distribution        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 1,899,179 1,562,867 2,937,234 2,647,027
Alternative revenue program revenues (20,117) 22,315 47,219 39,716
Other revenues 3,466 3,999 7,410 7,776
Total operating revenues 1,882,528 1,589,181 2,991,863 2,694,519
Operating Segments | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 270,773 225,321 539,466 443,668
Alternative revenue program revenues (11,774) (1,834) (25,077) (9,012)
Other revenues 0 0 0 0
Total operating revenues 258,999 223,487 514,389 434,656
Operating Segments | Gas sales revenues | Distribution        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 1,851,605 1,521,536 2,849,911 2,569,286
Operating Segments | Gas sales revenues | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 0 0 0 0
Operating Segments | Transportation revenues | Distribution        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 43,352 37,607 80,079 71,374
Operating Segments | Transportation revenues | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 266,514 223,159 532,543 438,464
Operating Segments | Miscellaneous revenues | Distribution        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 4,222 3,724 7,244 6,367
Operating Segments | Miscellaneous revenues | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 4,259 2,162 6,923 5,204
Operating Segments | Residential | Gas sales revenues | Distribution        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 1,308,691 1,065,296 2,001,741 1,792,978
Operating Segments | Residential | Gas sales revenues | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 0 0 0 0
Operating Segments | Commercial | Gas sales revenues | Distribution        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 480,108 404,701 746,162 681,954
Operating Segments | Commercial | Gas sales revenues | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 0 0 0 0
Operating Segments | Industrial | Gas sales revenues | Distribution        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 38,885 30,419 65,206 58,650
Operating Segments | Industrial | Gas sales revenues | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 0 0 0 0
Operating Segments | Public authority and other | Gas sales revenues | Distribution        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers 23,921 21,120 36,802 35,704
Operating Segments | Public authority and other | Gas sales revenues | Pipeline and Storage        
Disaggregation of Revenue [Line Items]        
Revenues from contracts with customers $ 0 $ 0 $ 0 $ 0
v3.25.1
Revenue and Accounts Receivable - Narrative (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended 36 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Nov. 30, 2023
Disaggregation of Revenue [Line Items]              
Percent of customers excluded       89.00%      
Reduction to bad debt expense $ (14,391) $ (12,797)   $ (23,015) $ (19,547)    
Recovery of uncollectible accounts, not yet been written off         $ 4,192    
Mississippi Public Service Commission              
Disaggregation of Revenue [Line Items]              
Recovery of uncollectible accounts, term     2 years       1 year
Reduction to bad debt expense     $ 13,900        
Recovery of uncollectible accounts, previously written off but not yet recovered through rates           $ 9,700  
Recovery of uncollectible accounts, not yet been written off     $ 4,200        
Pipeline and storage segment              
Disaggregation of Revenue [Line Items]              
Regulatory mechanism threshold       75.00%      
v3.25.1
Revenue and Accounts Receivable - Schedule of Rollforward of Allowance for Doubtful Accounts (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2025
Mar. 31, 2024
Accounts Receivable, Allowance for Credit Loss [Roll Forward]          
Beginning balance $ 39,166 $ 35,406 $ 40,840 $ 37,056 $ 40,840
Current period provisions 14,391 12,797   23,015 19,547
Write-offs charged against allowance (4,761) (5,859)   (12,209) (14,616)
Recoveries of amounts previously written off 545 361   1,479 1,126
Mississippi recovery of uncollectible accounts         (4,192)
Ending balance $ 49,341 $ 42,705 $ 35,406 $ 49,341 $ 42,705
v3.25.1
Debt - Schedule of Long-term Debt Instruments (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Sep. 30, 2024
Debt Instrument [Line Items]    
Long-term debt $ 8,435,000 $ 7,785,000
Finance lease obligations 48,075 48,890
Total long-term debt 8,483,075 7,833,890
Less:    
Original issue premium on unsecured senior notes and debentures (3,825) (9,071)
Debt issuance cost 61,463 57,664
Current maturities of long-term debt 11,712 1,651
Total long-term debt, net $ 8,413,725 7,783,646
Unsecured 3.00% Senior Notes, due June 2027    
Debt Instrument [Line Items]    
Interest rate 3.00%  
Long-term debt $ 500,000 500,000
Unsecured 2.625% Senior Notes, due September 2029    
Debt Instrument [Line Items]    
Interest rate 2.625%  
Long-term debt $ 500,000 500,000
Unsecured 1.50% Senior Notes, due January 2031    
Debt Instrument [Line Items]    
Interest rate 1.50%  
Long-term debt $ 600,000 600,000
Unsecured 5.45% Senior Notes, due October 2032    
Debt Instrument [Line Items]    
Interest rate 5.45%  
Long-term debt $ 300,000 300,000
Unsecured 5.90% Senior Notes, due November 2033    
Debt Instrument [Line Items]    
Interest rate 5.90%  
Long-term debt $ 725,000 725,000
Unsecured 5.95% Senior Notes, due October 2034    
Debt Instrument [Line Items]    
Interest rate 5.95%  
Long-term debt $ 200,000 200,000
Unsecured 5.50% Senior Notes, due June 2041    
Debt Instrument [Line Items]    
Interest rate 5.50%  
Long-term debt $ 400,000 400,000
Unsecured 4.15% Senior Notes, due January 2043    
Debt Instrument [Line Items]    
Interest rate 4.15%  
Long-term debt $ 500,000 500,000
Unsecured 4.125% Senior Notes, due October 2044    
Debt Instrument [Line Items]    
Interest rate 4.125%  
Long-term debt $ 750,000 750,000
Unsecured 4.30% Senior Notes, due October 2048    
Debt Instrument [Line Items]    
Interest rate 4.30%  
Long-term debt $ 600,000 600,000
Unsecured 4.125% Senior Notes, due March 2049    
Debt Instrument [Line Items]    
Interest rate 4.125%  
Long-term debt $ 450,000 450,000
Unsecured 3.375% Senior Notes, due September 2049    
Debt Instrument [Line Items]    
Interest rate 3.375%  
Long-term debt $ 500,000 500,000
Unsecured 2.85% Senior Notes, due February 2052    
Debt Instrument [Line Items]    
Interest rate 2.85%  
Long-term debt $ 600,000 600,000
Unsecured 5.75% Senior Notes, due October 2052    
Debt Instrument [Line Items]    
Interest rate 5.75%  
Long-term debt $ 500,000 500,000
Unsecured 6.20% Senior Notes, due November 2053    
Debt Instrument [Line Items]    
Interest rate 6.20%  
Long-term debt $ 500,000 500,000
Unsecured 5.00% Senior Notes, due December 2054    
Debt Instrument [Line Items]    
Interest rate 5.00%  
Long-term debt $ 650,000 0
Medium-term note Series A, 1995-1, 6.67%, due December 2025    
Debt Instrument [Line Items]    
Interest rate 6.67%  
Long-term debt $ 10,000 10,000
Unsecured 6.75% Debentures, due July 2028    
Debt Instrument [Line Items]    
Interest rate 6.75%  
Long-term debt $ 150,000 $ 150,000
v3.25.1
Debt - Narrative (Details)
 6 Months Ended
Oct. 01, 2024
USD ($)
Mar. 31, 2025
USD ($)
credit_facility
Mar. 31, 2024
USD ($)
Sep. 30, 2024
USD ($)
Line Of Credit Facility [Line Items]        
Proceeds from issuance of long-term debt   $ 645,372,000 $ 898,275,000  
Maximum debt-to-total-capitalization ratio   70.00%    
Debt-to-total-capitalization ratio   0.40    
Minimum        
Line Of Credit Facility [Line Items]        
Outstanding indebtedness   $ 15,000,000    
Maximum        
Line Of Credit Facility [Line Items]        
Outstanding indebtedness   $ 100,000,000    
Unsecured 5.00% Senior Notes, due December 2054        
Line Of Credit Facility [Line Items]        
Interest rate   5.00%    
Unsecured 5.00% Senior Notes, due December 2054 | Senior Notes        
Line Of Credit Facility [Line Items]        
Debt face amount $ 650,000,000      
Interest rate 5.00%      
Effective rate 3.90%      
Proceeds from issuance of long-term debt $ 639,400,000      
Five Year Unsecured Revolving Credit Agreement | Commercial Paper        
Line Of Credit Facility [Line Items]        
Maximum borrowing capacity   $ 1,500,000,000    
Debt agreement term   5 years    
Five Year Unsecured Revolving Credit Agreement, March 28, 2029        
Line Of Credit Facility [Line Items]        
Outstanding commercial paper   $ 0   $ 0
Five Year Unsecured Revolving Credit Agreement, March 28, 2029 | Minimum | Base Rate        
Line Of Credit Facility [Line Items]        
Interest rate spread   0.00%    
Five Year Unsecured Revolving Credit Agreement, March 28, 2029 | Minimum | Term SOFR        
Line Of Credit Facility [Line Items]        
Interest rate spread   0.75%    
Five Year Unsecured Revolving Credit Agreement, March 28, 2029 | Maximum | Base Rate        
Line Of Credit Facility [Line Items]        
Interest rate spread   0.25%    
Five Year Unsecured Revolving Credit Agreement, March 28, 2029 | Maximum | Term SOFR        
Line Of Credit Facility [Line Items]        
Interest rate spread   1.25%    
Five Year Unsecured Revolving Credit Agreement, March 28, 2029 | Commercial Paper        
Line Of Credit Facility [Line Items]        
Maximum borrowing capacity   $ 1,500,000,000    
Accordion feature   250,000,000    
Maximum borrowing capacity post accordion feature   1,750,000,000    
Five Year Unsecured Revolving Credit Agreement, March 28, 2029 | Revolving Credit Facility        
Line Of Credit Facility [Line Items]        
Maximum borrowing capacity   $ 3,100,000,000    
Number of credit facilities | credit_facility   4    
$1.5 Billion Revolving Credit Facility | Revolving Credit Facility        
Line Of Credit Facility [Line Items]        
Maximum borrowing capacity   $ 1,500,000,000    
Debt agreement term   3 years    
Accordion feature   $ 250,000,000    
Maximum borrowing capacity post accordion feature   1,750,000,000    
Outstanding borrowings   $ 0   0
$1.5 Billion Revolving Credit Facility | Revolving Credit Facility | Minimum | Base Rate        
Line Of Credit Facility [Line Items]        
Interest rate spread   0.00%    
$1.5 Billion Revolving Credit Facility | Revolving Credit Facility | Minimum | Term SOFR        
Line Of Credit Facility [Line Items]        
Interest rate spread   0.75%    
$1.5 Billion Revolving Credit Facility | Revolving Credit Facility | Maximum | Base Rate        
Line Of Credit Facility [Line Items]        
Interest rate spread   0.25%    
$1.5 Billion Revolving Credit Facility | Revolving Credit Facility | Maximum | Term SOFR        
Line Of Credit Facility [Line Items]        
Interest rate spread   1.25%    
$50 Million Bank Loan Agreement | Line of Credit        
Line Of Credit Facility [Line Items]        
Maximum borrowing capacity   $ 50,000,000    
Debt agreement term   364 days    
Outstanding borrowings   $ 0   $ 0
$50 Million Revolving Credit Facility        
Line Of Credit Facility [Line Items]        
Outstanding borrowings   0    
$50 Million Revolving Credit Facility | Revolving Credit Facility        
Line Of Credit Facility [Line Items]        
Maximum borrowing capacity   $ 50,000,000    
Debt agreement term   364 days    
Remaining borrowing capacity   $ 44,400,000    
v3.25.1
Shareholders' Equity - Schedule of Components of Equity (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Dec. 31, 2024
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2025
Mar. 31, 2024
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Common stock outstanding, beginning balance (in shares)   155,258,845     155,258,845  
Shareholders' equity, beginning balance $ 12,780,481 $ 12,157,669 $ 11,273,209 $ 10,870,064 $ 12,157,669 $ 10,870,064
Net income 485,576 351,858 432,023 311,292 837,434 743,315
Other comprehensive income (loss) (5,587) 16,423 27,108 (49,936) $ 10,836 (22,828)
Cash dividends (138,416) (135,453) (121,667) (119,898)    
Public and other stock offerings 3,841 383,537 4,025 257,768    
Stock-based compensation plans $ 12,070 6,447 3,941 3,919    
Common stock outstanding, ending balance (in shares) 158,835,123       158,835,123  
Shareholders' equity, ending balance $ 13,137,965 $ 12,780,481 $ 11,618,639 $ 11,273,209 $ 13,137,965 $ 11,618,639
Cash dividends per share (USD per share) $ 0.870 $ 0.87 $ 0.805 $ 0.805 $ 1.74 $ 1.61
Common stock            
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Common stock outstanding, beginning balance (in shares) 158,726,065 155,258,845 150,834,397 148,492,783 155,258,845 148,492,783
Shareholders' equity, beginning balance $ 794 $ 776 $ 754 $ 742 $ 776 $ 742
Public and other stock offerings (in shares) 26,367 3,329,358 34,687 2,177,864    
Public and other stock offerings   $ 17   $ 11    
Stock-based compensation plans (in shares) 82,691 137,862 5,468 163,750    
Stock-based compensation plans   $ 1   $ 1    
Common stock outstanding, ending balance (in shares) 158,835,123 158,726,065 150,874,552 150,834,397 158,835,123 150,874,552
Shareholders' equity, ending balance $ 794 $ 794 $ 754 $ 754 $ 794 $ 754
Additional Paid-in Capital            
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Shareholders' equity, beginning balance 7,864,525 7,474,559 6,945,795 6,684,120 7,474,559 6,684,120
Public and other stock offerings 3,841 383,520 4,025 257,757    
Stock-based compensation plans 12,070 6,446 3,941 3,918    
Shareholders' equity, ending balance 7,880,436 7,864,525 6,953,761 6,945,795 7,880,436 6,953,761
Accumulated Other Comprehensive Income (Loss)            
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Shareholders' equity, beginning balance 482,138 465,715 468,592 518,528 465,715 518,528
Other comprehensive income (loss) (5,587) 16,423 27,108 (49,936)    
Shareholders' equity, ending balance 476,551 482,138 495,700 468,592 476,551 495,700
Retained Earnings            
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Shareholders' equity, beginning balance 4,433,024 4,216,619 3,858,068 3,666,674 4,216,619 3,666,674
Net income 485,576 351,858 432,023 311,292    
Cash dividends (138,416) (135,453) (121,667) (119,898)    
Shareholders' equity, ending balance $ 4,780,184 $ 4,433,024 $ 4,168,424 $ 3,858,068 $ 4,780,184 $ 4,168,424
v3.25.1
Shareholders' Equity - Narrative (Details) - USD ($)
$ in Thousands
 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Dec. 03, 2024
Class of Stock [Line Items]      
Forward sales equity agreement, settlement in cash $ 1,659,625    
Net proceeds from equity issuances 379,490 $ 254,022  
Shelf Registration Statement      
Class of Stock [Line Items]      
Debt and equity securities authorized for issuance     $ 8,000,000
Debt and equity securities authorized for issuance value remaining $ 6,300,000    
At-The-Market      
Class of Stock [Line Items]      
Value of shares authorized for issuance     $ 1,700,000
Forward sales equity agreement (in shares) 4,609,043    
Forward sales equity agreement, settlement in cash $ 658,200    
Shares issued (in shares) 3,300,904    
Net proceeds from equity issuances $ 379,500    
Equity available for issuance $ 1,000,000    
v3.25.1
Shareholders' Equity - Schedule of Forward Sales Agreement (Details)
$ / shares in Units, $ in Thousands
 6 Months Ended
Mar. 31, 2025
USD ($)
$ / shares
shares
Forward Contract Indexed to Issuer's Equity [Line Items]  
Shares available (in shares) | shares 12,598,259
Net proceeds available | $ $ 1,659,625
Forward price (USD per share) | $ / shares $ 131.73
Forward Sales Equity Agreement Maturing Quarter Ended June 30, 2025  
Forward Contract Indexed to Issuer's Equity [Line Items]  
Shares available (in shares) | shares 630,514
Net proceeds available | $ $ 73,406
Forward price (USD per share) | $ / shares $ 116.42
Forward Sales Equity Agreement Maturing Quarter Ended September 30, 2025  
Forward Contract Indexed to Issuer's Equity [Line Items]  
Shares available (in shares) | shares 815,655
Net proceeds available | $ $ 96,313
Forward price (USD per share) | $ / shares $ 118.08
Forward Sales Equity Agreement Maturing Quarter Ended December 31, 2025  
Forward Contract Indexed to Issuer's Equity [Line Items]  
Shares available (in shares) | shares 2,344,567
Net proceeds available | $ $ 297,650
Forward price (USD per share) | $ / shares $ 126.95
Forward Sales Equity Agreement Maturing Quarter Ended March 31, 2026  
Forward Contract Indexed to Issuer's Equity [Line Items]  
Shares available (in shares) | shares 3,627,033
Net proceeds available | $ $ 463,284
Forward price (USD per share) | $ / shares $ 127.73
Forward Sales Equity Agreement Maturing Quarter June 30, 2026  
Forward Contract Indexed to Issuer's Equity [Line Items]  
Shares available (in shares) | shares 669,043
Net proceeds available | $ $ 89,150
Forward price (USD per share) | $ / shares $ 133.25
Forward Sales Equity Agreement Maturing Quarter December 31, 2026  
Forward Contract Indexed to Issuer's Equity [Line Items]  
Shares available (in shares) | shares 3,392,352
Net proceeds available | $ $ 472,749
Forward price (USD per share) | $ / shares $ 139.36
Forward Sales Equity Agreement Maturing Quarter March 31, 2027  
Forward Contract Indexed to Issuer's Equity [Line Items]  
Shares available (in shares) | shares 1,119,095
Net proceeds available | $ $ 167,073
Forward price (USD per share) | $ / shares $ 149.29
v3.25.1
Shareholders' Equity - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Dec. 31, 2024
Mar. 31, 2024
Dec. 31, 2023
Mar. 31, 2025
Mar. 31, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]            
Shareholders' equity, beginning balance $ 12,780,481 $ 12,157,669 $ 11,273,209 $ 10,870,064 $ 12,157,669 $ 10,870,064
Other comprehensive income (loss) before reclassifications         17,976 (17,845)
Amounts reclassified from accumulated other comprehensive income         (7,140) (4,983)
Total other comprehensive income (loss) (5,587) 16,423 27,108 (49,936) 10,836 (22,828)
Shareholders' equity, ending balance 13,137,965 12,780,481 11,618,639 11,273,209 13,137,965 11,618,639
Available- for-Sale Securities            
AOCI Attributable to Parent, Net of Tax [Roll Forward]            
Shareholders' equity, beginning balance   213   (369) 213 (369)
Other comprehensive income (loss) before reclassifications         (65) 246
Amounts reclassified from accumulated other comprehensive income         0 0
Total other comprehensive income (loss)         (65) 246
Shareholders' equity, ending balance 148   (123)   148 (123)
Interest Rate Agreement Cash Flow Hedges            
AOCI Attributable to Parent, Net of Tax [Roll Forward]            
Shareholders' equity, beginning balance   465,502   518,897 465,502 518,897
Other comprehensive income (loss) before reclassifications         18,041 (18,091)
Amounts reclassified from accumulated other comprehensive income         (7,140) (4,983)
Total other comprehensive income (loss)         10,901 (23,074)
Shareholders' equity, ending balance 476,403   495,823   476,403 495,823
Accumulated Other Comprehensive Income (Loss)            
AOCI Attributable to Parent, Net of Tax [Roll Forward]            
Shareholders' equity, beginning balance 482,138 465,715 468,592 518,528 465,715 518,528
Total other comprehensive income (loss) (5,587) 16,423 27,108 (49,936)    
Shareholders' equity, ending balance $ 476,551 $ 482,138 $ 495,700 $ 468,592 $ 476,551 $ 495,700
v3.25.1
Securitization - Narrative (Details) - USD ($)
$ in Thousands
 1 Months Ended
Mar. 31, 2023
Mar. 31, 2025
Sep. 30, 2024
Jun. 30, 2023
Variable Interest Entity [Line Items]        
Long-term debt, fair value   $ 7,568,621 $ 7,337,936  
Variable Interest Entity, Primary Beneficiary | Texas | Extraordinary Gas Cost | Winter Storm Uri        
Variable Interest Entity [Line Items]        
Regulatory asset, authorized $ 3,500,000      
Variable Interest Entity, Primary Beneficiary | Texas | Extraordinary Gas Cost | Winter Storm Uri | Minimum        
Variable Interest Entity [Line Items]        
Regulatory asset, maturity period 12 years      
Variable Interest Entity, Primary Beneficiary | Texas | Extraordinary Gas Cost | Winter Storm Uri | Maximum        
Variable Interest Entity [Line Items]        
Regulatory asset, maturity period 18 years      
Securitized Utility Tariff Bonds | Senior Notes | Variable Interest Entity, Primary Beneficiary        
Variable Interest Entity [Line Items]        
Debt face amount       $ 95,000
Long-term debt   81,000 85,100  
Long-term debt, fair value   $ 81,900 $ 87,800  
v3.25.1
Securitization - Schedule of Condensed Consolidated Balance Sheet (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Sep. 30, 2024
Variable Interest Entity [Line Items]    
Restricted cash and cash equivalents $ 1,616 $ 1,516
Other current assets 288,275 288,068
Securitized intangible asset, net 78,892 82,844
Current maturities of securitized long-term debt 8,418 8,207
Securitized long-term debt 72,609 76,871
Variable Interest Entity, Primary Beneficiary    
Variable Interest Entity [Line Items]    
Restricted cash and cash equivalents 1,616 1,516
Other current assets 3 3
Securitized intangible asset, net 78,892 82,844
Accrued interest 348 365
Current maturities of securitized long-term debt 8,418 8,207
Securitized long-term debt $ 72,609 $ 76,871
v3.25.1
Securitization - Schedule of Consolidated Statements of Comprehensive Income (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Variable Interest Entity [Line Items]        
Operating revenues $ 1,950,502 $ 1,647,227 $ 3,126,501 $ 2,805,694
Operation and maintenance expense (233,296) (199,899) (440,340) (366,244)
Amortization expense (182,750) (165,087) (363,283) (329,695)
Interest expense, net (50,014) (55,442) (102,939) (107,317)
Income before income taxes 603,097 512,235 1,034,286 877,351
Variable Interest Entity, Primary Beneficiary        
Variable Interest Entity [Line Items]        
Operating revenues 2,951 3,469 6,344 6,802
Operation and maintenance expense (216) (224) (277) (224)
Amortization expense (1,689) (2,103) (3,953) (4,269)
Interest expense, net (1,046) (1,142) (2,114) (2,309)
Income before income taxes $ 0 $ 0 $ 0 $ 0
v3.25.1
Interim Pension and Other Postretirement Benefit Plan Information - Schedule of Components of Net Periodic Pension Cost (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Pension Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 2,837 $ 2,405 $ 5,674 $ 4,794
Interest cost 6,663 7,430 13,326 14,926
Expected return on assets (7,655) (7,202) (15,309) (14,404)
Amortization of prior service cost (credit) 0 0 0 0
Amortization of actuarial (gain) loss 256 97 511 215
Settlements     0 776
Net periodic pension cost 2,101 2,730 4,202 6,307
Other Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 2,033 1,507 4,066 3,014
Interest cost 3,365 3,509 6,731 7,017
Expected return on assets (3,831) (3,128) (7,663) (6,256)
Amortization of prior service cost (credit) (3,260) (3,260) (6,520) (6,520)
Amortization of actuarial (gain) loss (2,429) (2,718) (4,858) (5,436)
Settlements     0 0
Net periodic pension cost $ (4,122) $ (4,090) $ (8,244) $ (8,181)
v3.25.1
Commitments and Contingencies (Details)
 6 Months Ended
Jan. 27, 2024
fatality
incident
Mar. 31, 2025
MMcf
Dec. 02, 2024
fatality
National Transportation Safety Board | Jackson, Mississippi      
Long-term Purchase Commitment [Line Items]      
Number of incidents investigated that occurred during period | incident 2    
Number of fatalities under investigation | fatality 1    
National Transportation Safety Board | Avondale, Louisiana      
Long-term Purchase Commitment [Line Items]      
Number of fatalities under investigation | fatality     1
Supply Commitment      
Long-term Purchase Commitment [Line Items]      
Contract term   1 year  
Supply Commitment | Short-term Contract with Customer      
Long-term Purchase Commitment [Line Items]      
Contract term   1 year  
Purchase commitment volume | MMcf   67,500  
Supply Commitment | Long-term Contract with Customer Within Two To Three Years      
Long-term Purchase Commitment [Line Items]      
Purchase commitment volume | MMcf   57,500  
Supply Commitment | Long-term Contract with Customer Within Two To Three Years | Minimum      
Long-term Purchase Commitment [Line Items]      
Contract term   2 years  
Supply Commitment | Long-term Contract with Customer Within Two To Three Years | Maximum      
Long-term Purchase Commitment [Line Items]      
Contract term   3 years  
v3.25.1
Income Taxes (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Sep. 30, 2024
Income Tax Contingency [Line Items]          
Effective income tax rate 19.50% 15.70% 19.00% 15.30%  
Regulatory liabilities $ 1,275,303   $ 1,275,303   $ 1,227,882
Regulatory excess deferred taxes          
Income Tax Contingency [Line Items]          
Deferred tax liabilities, net 178,600   178,600    
Regulatory liabilities 229,096   229,096   257,001
Regulatory excess deferred taxes | Other Current Liabilities          
Income Tax Contingency [Line Items]          
Deferred tax liabilities, net 73,900   73,900   $ 79,700
Regulatory excess deferred taxes, to be returned, tranche one          
Income Tax Contingency [Line Items]          
Deferred tax liabilities, net 115,500   $ 115,500    
Regulatory excess deferred taxes, to be returned, tranche one | Minimum          
Income Tax Contingency [Line Items]          
Return basis, term     12 months    
Regulatory excess deferred taxes, to be returned, tranche one | Maximum          
Income Tax Contingency [Line Items]          
Return basis, term     60 months    
Regulatory excess deferred taxes, to be returned, tranche two          
Income Tax Contingency [Line Items]          
Regulatory liabilities 48,600   $ 48,600    
Regulatory excess deferred taxes, to be returned, tranche two | Minimum          
Income Tax Contingency [Line Items]          
Return basis, term     15 years    
Regulatory excess deferred taxes, to be returned, tranche two | Maximum          
Income Tax Contingency [Line Items]          
Return basis, term     68 years    
Regulatory excess deferred taxes, to be returned, tranche three          
Income Tax Contingency [Line Items]          
Deferred tax liabilities, net $ 14,500   $ 14,500    
v3.25.1
Financial Instruments - Narrative (Details)
 3 Months Ended 6 Months Ended
Mar. 31, 2025
USD ($)
Mar. 31, 2024
USD ($)
Mar. 31, 2025
USD ($)
MMcf
Mar. 31, 2024
USD ($)
Sep. 30, 2024
USD ($)
Derivative [Line Items]          
Purchase commitment volume | MMcf     4,017    
Contract netting $ 0   $ 0   $ 0
Cash collateral 0   0   $ 0
Net (gain) loss on settled interest rate agreements (5,100,000) $ (3,200,000) (10,200,000) $ (6,400,000)  
Net realized gains in AOCI $ 387,000,000.0   $ 387,000,000.0    
Designated As Hedge | Gas Purchases | Commodity contracts          
Derivative [Line Items]          
Purchase commitment volume | MMcf     24,000.0    
Designated As Hedge | Gas Purchases | Commodity contracts | Minimum          
Derivative [Line Items]          
Hedging percent 25.00%   25.00%    
Designated As Hedge | Gas Purchases | Commodity contracts | Maximum          
Derivative [Line Items]          
Hedging percent 50.00%   50.00%    
v3.25.1
Financial Instruments - Schedule of Interest Rate Risk Management Activities (Details) - Cash Flow Hedging - Designated As Hedge
$ in Thousands
Mar. 31, 2025
USD ($)
Forward Interest Rate Swap  
Derivative [Line Items]  
Derivative notional amount $ 300,000
Forward Interest Rate Swap, Planned Issued Fiscal 2026  
Derivative [Line Items]  
Derivative notional amount $ 300,000
v3.25.1
Financial Instruments - Schedule of Derivative Instruments in Statement of Financial Position, Fair Value (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Sep. 30, 2024
Derivatives Fair Value [Line Items]    
Gross/net financial instruments, assets $ 123,209 $ 96,288
Gross/net financial instruments, liabilities (561) (7,637)
Designated As Hedges:    
Derivatives Fair Value [Line Items]    
Gross/net financial instruments, assets 114,996 91,981
Gross/net financial instruments, liabilities 0 0
Designated As Hedges: | Interest rate contracts    
Derivatives Fair Value [Line Items]    
Gross/net financial instruments, assets 114,996 91,981
Gross/net financial instruments, liabilities 0 0
Not Designated As Hedges:    
Derivatives Fair Value [Line Items]    
Gross/net financial instruments, assets 8,213 4,307
Gross/net financial instruments, liabilities (561) (7,637)
Not Designated As Hedges: | Other current assets | Commodity contracts    
Derivatives Fair Value [Line Items]    
Gross/net financial instruments, assets 8,213 2,091
Not Designated As Hedges: | Other current liabilities | Commodity contracts    
Derivatives Fair Value [Line Items]    
Gross/net financial instruments, liabilities $ (561) (7,324)
Not Designated As Hedges: | Deferred charges and other assets | Commodity contracts    
Derivatives Fair Value [Line Items]    
Gross/net financial instruments, assets   2,216
Not Designated As Hedges: | Deferred credits and other liabilities | Commodity contracts    
Derivatives Fair Value [Line Items]    
Gross/net financial instruments, liabilities   $ (313)
v3.25.1
Financial Instruments - Schedule of Cash Flow Hedges Included in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Increase (decrease) in fair value:        
Interest rate agreements $ (1,678) $ 29,650 $ 18,041 $ (18,091)
Recognition of (gains) losses in earnings due to settlements:        
Interest rate agreements (3,982) (2,492) (7,140) (4,983)
Total other comprehensive income (loss) from hedging, net of tax $ (5,660) $ 27,158 $ 10,901 $ (23,074)
v3.25.1
Financial Instruments - Schedule Of Expected Deferred Gains (Losses) Recognition (Details)
$ in Thousands
 6 Months Ended
Mar. 31, 2025
USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Next twelve months $ 15,925
Thereafter 371,080
Total $ 387,005
v3.25.1
Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Sep. 30, 2024
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Financial instruments net assets $ 123,209 $ 96,288
Total debt and equity securities 109,049 110,594
Total assets 232,258 206,882
Financial instruments net liability 561 7,637
Registered investment companies    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 27,787 28,311
Bond mutual funds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 40,955 40,341
Bonds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Debt securities 37,118 39,142
Money market funds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 3,189 2,800
Quoted Prices in Active Markets (Level 1)    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Financial instruments gross assets 0 0
Total debt and equity securities 68,742 68,652
Total assets 68,742 68,652
Financial instruments gross liability 0 0
Quoted Prices in Active Markets (Level 1) | Registered investment companies    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 27,787 28,311
Quoted Prices in Active Markets (Level 1) | Bond mutual funds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 40,955 40,341
Quoted Prices in Active Markets (Level 1) | Bonds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Debt securities 0 0
Quoted Prices in Active Markets (Level 1) | Money market funds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 0 0
Significant Other Observable Inputs (Level 2)    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Financial instruments gross assets 123,209 96,288
Total debt and equity securities 40,307 41,942
Total assets 163,516 138,230
Financial instruments gross liability 561 7,637
Significant Other Observable Inputs (Level 2) | Registered investment companies    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 0 0
Significant Other Observable Inputs (Level 2) | Bond mutual funds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 0 0
Significant Other Observable Inputs (Level 2) | Bonds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Debt securities 37,118 39,142
Significant Other Observable Inputs (Level 2) | Money market funds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 3,189 2,800
Significant Other Unobservable Inputs (Level 3)    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Financial instruments gross assets 0 0
Total debt and equity securities 0 0
Total assets 0 0
Financial instruments gross liability 0 0
Significant Other Unobservable Inputs (Level 3) | Registered investment companies    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 0 0
Significant Other Unobservable Inputs (Level 3) | Bond mutual funds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities 0 0
Significant Other Unobservable Inputs (Level 3) | Bonds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Debt securities 0 0
Significant Other Unobservable Inputs (Level 3) | Money market funds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Equity securities $ 0 $ 0
v3.25.1
Fair Value Measurements - Narrative (Details) - USD ($)
Mar. 31, 2025
Sep. 30, 2024
Fair Value Disclosures [Abstract]    
Allowance for credit losses $ 0  
Cost basis $ 36,900,000 $ 38,900,000
v3.25.1
Fair Value Measurements - Schedule of Debt Instruments (Details) - USD ($)
$ in Thousands
Mar. 31, 2025
Sep. 30, 2024
Fair Value Disclosures [Abstract]    
Carrying Amount $ 8,435,000 $ 7,785,000
Fair Value $ 7,568,621 $ 7,337,936