Atmos Energy (ATO) 10-Q 5 May 21 2021 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
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)		130,671,944
Entity Central Index Key	0000731802
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
ASSETS
Property, plant and equipment	$ 16,752,585	$ 15,957,221
Less accumulated depreciation and amortization	2,712,997	2,601,874
Net property, plant and equipment	14,039,588	13,355,347
Current assets
Cash and cash equivalents	865,311	20,808
Accounts receivable, net	469,595	230,595
Gas stored underground	50,043	111,950
Other current assets	235,485	107,905
Total current assets	1,620,434	471,258
Goodwill	731,257	731,257
Deferred charges and other assets (See Note 8)	3,017,531	801,170
Total assets	19,408,810	15,359,032
Shareholders’ equity
Common stock, no par value (stated at $0.005 per share); 200,000,000 shares authorized; issued and outstanding: 2021 — 125,882,477 shares; 2020 — 125,882,477 shares	653	629
Additional paid-in capital	4,853,703	4,377,149
Accumulated other comprehensive income (loss)	140,471	(57,589)
Retained earnings	2,826,098	2,471,014
Shareholders’ equity	7,820,925	6,791,203
Long-term debt	7,316,404	4,531,779
Total capitalization	15,137,329	11,322,982
Current liabilities
Accounts payable and accrued liabilities	263,597	235,775
Other current liabilities	607,525	546,461
Current maturities of long-term debt	177	165
Total current liabilities	871,299	782,401
Deferred income taxes	1,658,000	1,456,569
Regulatory excess deferred taxes	639,496	697,764
Regulatory cost of removal obligation	465,104	457,188
Deferred credits and other liabilities	637,582	642,128
Total shareholders' equity and liabilities	$ 19,408,810	$ 15,359,032

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2021	Sep. 30, 2020
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)	130,667,109	125,882,477
Common stock outstanding (in shares)	130,667,109	125,882,477

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Operating revenues	$ 1,319,073	$ 977,665	$ 2,233,553	$ 1,853,228
Purchased gas cost	573,809	317,883	862,069	614,751
Operation and maintenance expense	156,375	147,824	295,018	300,069
Depreciation and amortization expense	118,636	105,916	233,921	210,978
Taxes, other than income	88,449	74,604	161,901	143,211
Operating income	381,804	331,438	680,644	584,219
Other non-operating income (expense)	2,834	(2,989)	8,906	1,898
Interest charges	26,096	22,171	48,106	49,400
Income before income taxes	358,542	306,278	641,444	536,717
Income tax expense	61,788	66,632	127,012	118,398
Net income	$ 296,754	$ 239,646	$ 514,432	$ 418,319
Basic net income per share (USD per share)	$ 2.30	$ 1.95	$ 4.01	$ 3.43
Diluted net income per share (USD per share)	2.30	1.95	4.01	3.42
Cash dividends per share (USD per share)	$ 0.625	$ 0.575	$ 1.25	$ 1.15
Basic weighted average shares outstanding (in shares)	129,161	122,916	128,098	122,015
Diluted weighted average shares outstanding (in shares)	129,164	122,997	128,100	122,179
Other comprehensive income (loss), net of tax
Net unrealized holding gains on available-for-sale securities, net of tax	$ (66)	$ (163)	$ (129)	$ (164)
Cash flow hedges:
Amortization and unrealized loss on interest rate agreements, net of tax	138,005	1,053	198,189	2,106
Total other comprehensive income (loss)	137,939	890	198,060	1,942
Total comprehensive income	434,693	240,536	712,492	420,261
Distribution segment
Operating revenues	1,281,826	932,296	2,157,713	1,760,136
Pipeline and storage segment
Operating revenues	37,247	45,369	75,840	93,092
Operating Segments | Distribution segment
Operating revenues	1,282,674	933,005	2,159,324	1,761,509
Purchased gas cost	691,147	418,935	1,102,219	816,493
Operation and maintenance expense	123,990	115,851	232,792	230,203
Depreciation and amortization expense	85,667	76,265	168,537	152,339
Taxes, other than income	78,615	68,413	142,967	128,656
Operating income	303,255	253,541	512,809	433,818
Other non-operating income (expense)	(760)	(5,191)	75	(3,237)
Income before income taxes	288,478	237,553	488,155	403,422
Income tax expense	56,142	50,489	102,127	86,601
Net income	232,336	187,064	386,028	316,821
Operating Segments | Pipeline and storage segment
Operating revenues	154,168	146,237	313,881	294,413
Purchased gas cost	113	202	(1,131)	301
Operation and maintenance expense	32,703	32,296	62,859	70,517
Depreciation and amortization expense	32,969	29,651	65,384	58,639
Taxes, other than income	9,834	6,191	18,934	14,555
Operating income	78,549	77,897	167,835	150,401
Other non-operating income (expense)	3,594	2,202	8,831	5,135
Income before income taxes	70,064	68,725	153,289	133,295
Income tax expense	5,646	16,143	24,885	31,797
Net income	64,418	52,582	128,404	101,498
Eliminations
Operating revenues	(117,769)	(101,577)	(239,652)	(202,694)
Purchased gas cost	(117,451)	(101,254)	(239,019)	(202,043)
Operation and maintenance expense	(318)	(323)	(633)	(651)
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
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	848	709	1,611	1,373
Eliminations | Pipeline and storage segment
Operating revenues	116,921	100,868	238,041	201,321
Purchased gas cost
Purchased gas cost	573,809	317,883	862,069	614,751
Purchased gas cost | Operating Segments | Distribution segment
Purchased gas cost	691,147	418,935	1,102,219	816,493
Purchased gas cost | Operating Segments | Pipeline and storage segment
Purchased gas cost	113	202	(1,131)	301
Purchased gas cost | Eliminations
Purchased gas cost	$ (117,451)	$ (101,254)	$ (239,019)	$ (202,043)

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Net unrealized holding losses on available-for-sale securities, tax	$ (19)	$ (49)	$ (37)	$ (49)
Amortization and unrealized gain (loss) on interest rate agreements, tax	$ 39,887	$ 312	$ 57,282	$ 623

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows From Operating Activities
Net income	$ 514,432	$ 418,319
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization expense	233,921	210,978
Deferred income taxes	128,725	110,664
Other	(938)	7,144
Net assets / liabilities from risk management activities	(1,954)	1,310
Increase (Decrease) in Regulatory Assets Related To Storm	(2,093,534)	0
Net change in other operating assets and liabilities	(182,898)	(114,640)
Net cash provided by (used in) operating activities	(1,402,246)	633,775
Cash Flows From Investing Activities
Capital expenditures	(845,728)	(994,737)
Debt and equity securities activities, net	(5,506)	(1,131)
Other, net	5,171	4,631
Net cash used in investing activities	(846,063)	(991,237)
Cash Flows From Financing Activities
Net decrease in short-term debt	0	(264,992)
Net proceeds from equity offering	460,678	258,047
Issuance of common stock through stock purchase and employee retirement plans	8,291	8,321
Proceeds from issuance of long-term debt	2,797,346	799,450
Cash dividends paid	(159,348)	(140,077)
Debt issuance costs	(14,155)	(7,738)
Net cash provided by financing activities	3,092,812	653,011
Net increase in cash and cash equivalents	844,503	295,549
Cash and cash equivalents at beginning of period	20,808	24,550
Cash and cash equivalents at end of period	$ 865,311	$ 320,099

Nature of Business

Nature of Business	6 Months Ended
	Mar. 31, 2021
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 three million residential, commercial, public authority and industrial customers through our six regulated distribution divisions, which at March 31, 2021, 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.

Unaudited Financial Information

Unaudited Financial Information	6 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Unaudited Financial Information	Unaudited Financial Information These consolidated interim-period financial statements have been prepared in accordance with accounting principles generally accepted in the United States on the same basis, aside from accounting policy changes noted below, 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, 2020. 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, 2020. Because of seasonal and other factors, the results of operations for the six-month period ended March 31, 2021 are not indicative of our results of operations for the full 2021 fiscal year, which ends September 30, 2021. Except as described in Note 6 and Note 8 to the unaudited condensed consolidated financial statements regarding recent activity related to our revolving credit facilities and securitization legislation, no events have occurred subsequent to the balance sheet date that would require recognition or disclosure in the unaudited condensed consolidated financial statements. Significant accounting policies Except as noted below, related to the change in policies as a result of our adoption of new accounting standards, 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, 2020. During the second quarter of fiscal 2021, we completed our goodwill impairment assessment. 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. Accounting pronouncements adopted in fiscal 2021 Effective October 1, 2020, we adopted new accounting guidance that requires credit losses on most financial assets measured at amortized cost and certain other instruments to be measured using an expected credit loss model. Under this model, we estimate credit losses over the entire contractual term of the instrument from the date of initial recognition of that instrument. The new guidance also introduces a new impairment recognition model for available-for-sale debt securities that will require credit losses to be recorded through an allowance account. We adopted the new guidance using a modified retrospective method. The adoption of this standard did not have a material impact on our financial position, results of operations and cash flows and no adjustments were made to October 1, 2020 opening balances as a result of this adoption. As required under the modified retrospective method of adoption, results for the reporting period beginning after October 1, 2020 are presented under Accounting Standards Codification (ASC) 326, while prior period amounts are not adjusted. See Notes 5 and 12 to the unaudited condensed consolidated financial statements for further discussion of implementation of the standard. Accounting pronouncements that will be effective after fiscal 2021 In March 2020, the Financial Accounting Standards Board (FASB) issued optional guidance which will ease the potential burden in accounting for or recognizing the effects of reference rate reform on financial reporting. The amendments provide optional expedients and exceptions for applying U.S. GAAP to contracts, hedging relationships and other transactions affected by the cessation of the London Interbank Offered Rate (LIBOR). The amendments can be elected immediately, as of March 12, 2020, through December 31, 2022. We are currently evaluating if we will apply the optional guidance as we assess the impact of the cessation of LIBOR on our current contracts and hedging relationships and the potential impact on our financial position, results of operations and cash flows. Regulatory assets and liabilities 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 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. Significant regulatory assets and liabilities as of March 31, 2021 and September 30, 2020 included the following: March 31, September 30, (In thousands) Regulatory assets: Pension and postretirement benefit costs $ 143,685 $ 149,089 Infrastructure mechanisms (1) 189,154 183,943 Winter Storm Uri incremental costs (2) 2,093,534 — Deferred gas costs 19,636 40,593 Recoverable loss on reacquired debt 4,165 4,894 Deferred pipeline record collection costs 30,415 29,839 Other 6,093 6,283 $ 2,486,682 $ 414,641 Regulatory liabilities: Regulatory excess deferred taxes (3) $ 702,393 $ 718,651 Regulatory cost of removal obligation 531,625 531,096 Deferred gas costs 122,864 19,985 Asset retirement obligation 20,348 20,348 APT annual adjustment mechanism 44,291 57,379 Other 25,828 19,554 $ 1,447,349 $ 1,367,013 (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) Includes extraordinary gas costs incurred during Winter Storm Uri and related carrying costs. See Note 8 to the unaudited condensed consolidated financial statements for further information. This amount is recorded within deferred charges and other assets on the condensed consolidated balance sheet as of March 31, 2021. (3) Includes amount from the remeasurement of the net deferred tax liability included in our rate base as a result of the Tax Cuts and Jobs Act of 2017 (the "TCJA") and a Kansas legislative change enacted in fiscal 2020. Of this amount, $62.9 million as of March 31, 2021 and $20.9 million as of September 30, 2020 is recorded in other current liabilities. These liabilities are currently being returned to customers in most of our jurisdictions on a provisional basis over 15 to 69 years until formal orders establish the final refund periods. During the six months ended March 31, 2021, our effective income tax rate decreased from 22.1% to 19.8%, primarily due to the approval of the amortization of excess deferred income taxes to APT customers. As of March 31, 2021, we received regulatory orders in most states to defer into a regulatory asset all expenses, beyond the normal course of business, related to Coronavirus Disease 2019 (COVID-19 or virus), including bad debt expense. As of March 31, 2021, no amounts have been recorded as regulatory assets or liabilities for expenses related to COVID-19.

Segment Information

Segment Information	6 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Segment Information	Segment Information We manage and review our consolidated operations through the following reportable segments: • The distribution segment is primarily comprised of our regulated natural gas distribution and related sales operations in eight states. • The pipeline and storage segment is comprised primarily of the 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, 2020. Income statements and capital expenditures for the three and six months ended March 31, 2021 and 2020 by segment are presented in the following tables: Three Months Ended March 31, 2021 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Operating revenues from external parties $ 1,281,826 $ 37,247 $ — $ 1,319,073 Intersegment revenues 848 116,921 (117,769) — Total operating revenues 1,282,674 154,168 (117,769) 1,319,073 Purchased gas cost 691,147 113 (117,451) 573,809 Operation and maintenance expense 123,990 32,703 (318) 156,375 Depreciation and amortization expense 85,667 32,969 — 118,636 Taxes, other than income 78,615 9,834 — 88,449 Operating income 303,255 78,549 — 381,804 Other non-operating income (expense) (760) 3,594 — 2,834 Interest charges 14,017 12,079 — 26,096 Income before income taxes 288,478 70,064 — 358,542 Income tax expense 56,142 5,646 — 61,788 Net income $ 232,336 $ 64,418 $ — $ 296,754 Capital expenditures $ 296,184 $ 92,735 $ — $ 388,919 Three Months Ended March 31, 2020 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Operating revenues from external parties $ 932,296 $ 45,369 $ — $ 977,665 Intersegment revenues 709 100,868 (101,577) — Total operating revenues 933,005 146,237 (101,577) 977,665 Purchased gas cost 418,935 202 (101,254) 317,883 Operation and maintenance expense 115,851 32,296 (323) 147,824 Depreciation and amortization expense 76,265 29,651 — 105,916 Taxes, other than income 68,413 6,191 — 74,604 Operating income 253,541 77,897 — 331,438 Other non-operating income (expense) (5,191) 2,202 — (2,989) Interest charges 10,797 11,374 — 22,171 Income before income taxes 237,553 68,725 — 306,278 Income tax expense 50,489 16,143 — 66,632 Net income $ 187,064 $ 52,582 $ — $ 239,646 Capital expenditures $ 373,313 $ 92,238 $ — $ 465,551 Six Months Ended March 31, 2021 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Operating revenues from external parties $ 2,157,713 $ 75,840 $ — $ 2,233,553 Intersegment revenues 1,611 238,041 (239,652) — Total operating revenues 2,159,324 313,881 (239,652) 2,233,553 Purchased gas cost 1,102,219 (1,131) (239,019) 862,069 Operation and maintenance expense 232,792 62,859 (633) 295,018 Depreciation and amortization expense 168,537 65,384 — 233,921 Taxes, other than income 142,967 18,934 — 161,901 Operating income 512,809 167,835 — 680,644 Other non-operating income 75 8,831 — 8,906 Interest charges 24,729 23,377 — 48,106 Income before income taxes 488,155 153,289 — 641,444 Income tax expense 102,127 24,885 — 127,012 Net income $ 386,028 $ 128,404 $ — $ 514,432 Capital expenditures $ 602,200 $ 243,528 $ — $ 845,728 Six Months Ended March 31, 2020 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Operating revenues from external parties $ 1,760,136 $ 93,092 $ — $ 1,853,228 Intersegment revenues 1,373 201,321 (202,694) — Total operating revenues 1,761,509 294,413 (202,694) 1,853,228 Purchased gas cost 816,493 301 (202,043) 614,751 Operation and maintenance expense 230,203 70,517 (651) 300,069 Depreciation and amortization expense 152,339 58,639 — 210,978 Taxes, other than income 128,656 14,555 — 143,211 Operating income 433,818 150,401 — 584,219 Other non-operating income (expense) (3,237) 5,135 — 1,898 Interest charges 27,159 22,241 — 49,400 Income before income taxes 403,422 133,295 — 536,717 Income tax expense 86,601 31,797 — 118,398 Net income $ 316,821 $ 101,498 $ — $ 418,319 Capital expenditures $ 777,560 $ 217,177 $ — $ 994,737 Balance sheet information at March 31, 2021 and September 30, 2020 by segment is presented in the following tables: March 31, 2021 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Property, plant and equipment, net $ 10,465,072 $ 3,574,516 $ — $ 14,039,588 Total assets $ 18,661,545 $ 3,799,037 $ (3,051,772) $ 19,408,810 September 30, 2020 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Property, plant and equipment, net $ 9,944,978 $ 3,410,369 $ — $ 13,355,347 Total assets $ 14,578,176 $ 3,647,907 $ (2,867,051) $ 15,359,032

Earnings Per Share

Earnings Per Share	6 Months Ended
	Mar. 31, 2021
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 7 to the unaudited condensed consolidated financial statements, when the impact is dilutive. Basic and diluted earnings per share for the three and six months ended March 31, 2021 and 2020 are calculated as follows: Three Months Ended March 31 Six Months Ended March 31 2021 2020 2021 2020 (In thousands, except per share amounts) Basic Earnings Per Share Net income $ 296,754 $ 239,646 $ 514,432 $ 418,319 Less: Income allocated to participating securities 199 178 350 314 Income available to common shareholders $ 296,555 $ 239,468 $ 514,082 $ 418,005 Basic weighted average shares outstanding 129,161 122,916 128,098 122,015 Net income per share — Basic $ 2.30 $ 1.95 $ 4.01 $ 3.43 Diluted Earnings Per Share Income available to common shareholders $ 296,555 $ 239,468 $ 514,082 $ 418,005 Effect of dilutive shares — — — — Income available to common shareholders $ 296,555 $ 239,468 $ 514,082 $ 418,005 Basic weighted average shares outstanding 129,161 122,916 128,098 122,015 Dilutive shares 3 81 2 164 Diluted weighted average shares outstanding 129,164 122,997 128,100 122,179 Net income per share - Diluted $ 2.30 $ 1.95 $ 4.01 $ 3.42

Revenue and Accounts Receivable

Revenue and Accounts Receivable	6 Months Ended
	Mar. 31, 2021
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, 2020. 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, 2021 and 2020. Three Months Ended March 31, 2021 Three Months Ended March 31, 2020 Distribution Pipeline and Storage Distribution Pipeline and Storage (In thousands) Gas sales revenues: Residential $ 893,720 $ — $ 596,315 $ — Commercial 326,182 — 230,779 — Industrial 31,066 — 25,628 — Public authority and other 20,227 — 14,662 — Total gas sales revenues 1,271,195 — 867,384 — Transportation revenues 30,973 151,565 28,504 154,748 Miscellaneous revenues 3,325 3,878 6,986 1,335 Revenues from contracts with customers 1,305,493 155,443 902,874 156,083 Alternative revenue program revenues (1) (23,313) (1,275) 29,638 (9,846) Other revenues 494 — 493 — Total operating revenues $ 1,282,674 $ 154,168 $ 933,005 $ 146,237 Six Months Ended March 31, 2021 Six Months Ended March 31, 2020 Distribution Pipeline and Storage Distribution Pipeline and Storage (In thousands) Gas sales revenues: Residential $ 1,485,554 $ — $ 1,148,391 $ — Commercial 535,129 — 442,093 — Industrial 55,774 — 50,553 — Public authority and other 33,289 — 27,684 — Total gas sales revenues 2,109,746 — 1,668,721 — Transportation revenues 58,740 316,326 55,144 306,758 Miscellaneous revenues 5,721 9,026 13,772 6,490 Revenues from contracts with customers 2,174,207 325,352 1,737,637 313,248 Alternative revenue program revenues (1) (15,872) (11,471) 22,887 (18,835) Other revenues 989 — 985 — Total operating revenues $ 2,159,324 $ 313,881 $ 1,761,509 $ 294,413 (1) In our distribution segment, we have weather-normalization adjustment mechanisms that serve to mitigate the effects of weather on our revenue. Additionally, 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 regulatorily determined revenue benchmark. 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. The receivable balances are short term and generally do not extend beyond one month. To minimize credit risk, we assess the credit worthiness of new customers, require deposits where necessary, assess late fees, pursue collection activities and disconnect service for nonpayment. After disconnection, accounts are written off when deemed uncollectible. As described in Note 2 to the unaudited condensed consolidated financial statements, on October 1, 2020, we adopted new accounting guidance which requires credit losses on our accounts receivable to be measured using an expected credit loss model over the entire contractual term from the date of initial recognition. At each reporting period, we assess the allowance for uncollectible accounts based on historical experience, current conditions and consideration of expected future conditions. Circumstances which could affect our estimates include, but are not limited to, customer credit issues, the level of natural gas prices, customer deposits and general economic conditions. Due to the COVID-19 pandemic, in March 2020 we temporarily suspended disconnecting customers for nonpayment and stopped charging late fees. We are actively working with our customers experiencing financial hardship to offer flexible payment options and directing them to aid agencies for financial assistance. Our allowance for uncollectible accounts reflects the expected impact on our customers’ ability to pay when we resume disconnection activity. Rollforwards of our allowance for uncollectible accounts for the three and six months ended March 31, 2021 are presented in the table below. The allowance excludes the gas cost portion of customers’ bills for approximately 78 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. Three Months Ended March 31, 2021 (In thousands) Beginning balance, December 31, 2020 $ 35,089 Current period provisions 11,532 Write-offs charged against allowance (2,381) Recoveries of amounts previously written off 440 Ending balance, March 31, 2021 $ 44,680 Six Months Ended March 31, 2021 (In thousands) Beginning balance, September 30, 2020 $ 29,949 Current period provisions 18,469 Write-offs charged against allowance (4,669) Recoveries of amounts previously written off 931 Ending balance, March 31, 2021 $ 44,680

Debt

Debt	6 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Debt	DebtThe nature and terms of our debt instruments and credit facilities are described in detail in Note 7 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020. Other than as described below, there were no material changes in the terms of our debt instruments during the six months ended March 31, 2021. Long-term debt at March 31, 2021 and September 30, 2020 consisted of the following: March 31, 2021 September 30, 2020 (In thousands) Unsecured 0.625% Senior Notes, due 2023 $ 1,100,000 $ — Unsecured 3.00% Senior Notes, due 2027 500,000 500,000 Unsecured 2.625% Senior Notes, due 2029 300,000 300,000 Unsecured 1.50% Senior Notes, due 2031 600,000 — Unsecured 5.95% Senior Notes, due 2034 200,000 200,000 Unsecured 5.50% Senior Notes, due 2041 400,000 400,000 Unsecured 4.15% Senior Notes, due 2043 500,000 500,000 Unsecured 4.125% Senior Notes, due 2044 750,000 750,000 Unsecured 4.30% Senior Notes, due 2048 600,000 600,000 Unsecured 4.125% Senior Notes, due 2049 450,000 450,000 Unsecured 3.375% Senior Notes, due 2049 500,000 500,000 Floating-rate term loan, due April 2022 200,000 200,000 Floating-rate Senior Notes, due 2023 1,100,000 — Medium-term note Series A, 1995-1, 6.67%, due 2025 10,000 10,000 Unsecured 6.75% Debentures, due 2028 150,000 150,000 Finance lease obligations 8,612 8,631 Total long-term debt 7,368,612 4,568,631 Less: Original issue discount on unsecured senior notes and debentures 3,030 583 Debt issuance cost 49,001 36,104 Current maturities 177 165 $ 7,316,404 $ 4,531,779 On March 9, 2021, we completed a public offering of $1.1 billion of 0.625% senior notes due 2023, with an effective interest rate of 0.834%, after giving effect to the offering costs, and $1.1 billion floating rate senior notes due 2023 that bear interest at a rate equal to the the Three-Month LIBOR rate plus 0.38%. The net proceeds from the offering, after the underwriting discount and offering expenses of $2.2 billion, were used for the payment of unplanned natural gas costs incurred during Winter Storm Uri. See Note 8 to the unaudited condensed consolidated financial statements for further information. The notes are subject to optional redemption at any time on or after September 9, 2021 at a price equal to 100 percent of the principal amount of the notes being redeemed, plus any accrued and unpaid interest thereon, if any, to, but excluding, the redemption date. On October 1, 2020, we completed a public offering of $600 million of 1.50% senior notes due 2031, with an effective interest rate of 1.71%, 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 $592.3 million, were used for general corporate purposes, including the repayment of working capital borrowings pursuant to our commercial paper program and the related settlement of our interest rate swaps. 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 with an equity-to-total-capitalization ratio between 50% and 60%, inclusive of long-term and short-term debt. 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 $2.5 billion of total working capital funding. The primary source of our funding is our commercial paper program, which is supported by a five-year unsecured $1.5 billion credit facility that was replaced on March 31, 2021, with a new five-year unsecured $1.5 billion credit facility that expires on March 31, 2026. The new facility bears interest at a base rate or at a LIBOR-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 LIBOR-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, 2021 and September 30, 2020, there were no amounts outstanding under our commercial paper program. We had a $600 million 364-day unsecured revolving credit facility, which was replaced on March 31, 2021, with a new $900 million three-year unsecured revolving credit facility. This new facility will be used primarily to provide additional working capital funding. The new facility bears interest at a base rate or at a LIBOR-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 LIBOR-based advances, based on the Company's credit ratings. Additionally, the facility contains a $100 million accordion feature, which provides the opportunity to increase the total committed loan to $1.0 billion. At March 31, 2021, there were no borrowings outstanding under this facility. Additionally, we have a $50 million 364-day unsecured facility, which was renewed April 1, 2021 and is used to provide working capital funding. There were no borrowings outstanding under this facility as of March 31, 2021. Finally, we have a $50 million 364-day unsecured revolving credit facility, which was renewed April 29, 2021 and is used to issue letters of credit and to provide working capital funding. At March 31, 2021, 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, 2021, our total-debt-to-total-capitalization ratio, as defined in the agreements, was 49 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, 2021. 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.

Shareholders' Equity

Shareholders' Equity	6 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Shareholders' Equity	Shareholders' EquityThe following tables present a reconciliation of changes in stockholders' equity for the three and six months ended March 31, 2021 and 2020. Common stock Additional Accumulated Retained Total Number of Stated (In thousands, except share and per share data) Balance, September 30, 2020 125,882,477 $ 629 $ 4,377,149 $ (57,589) $ 2,471,014 $ 6,791,203 Net income — — — — 217,678 217,678 Other comprehensive income — — — 60,121 — 60,121 Cash dividends ($0.625 per share) — — — — (79,023) (79,023) Common stock issued: Public and other stock offerings 2,126,118 11 219,998 — — 220,009 Stock-based compensation plans 144,366 1 3,167 — — 3,168 Balance, December 31, 2020 128,152,961 641 4,600,314 2,532 2,609,669 7,213,156 Net income — — — — 296,754 296,754 Other comprehensive income — — — 137,939 — 137,939 Cash dividends ($0.625 per share) — — — — (80,325) (80,325) Common stock issued: Public and other stock offerings 2,498,026 12 248,948 — — 248,960 Stock-based compensation plans 16,122 — 4,441 — — 4,441 Balance, March 31, 2021 130,667,109 $ 653 $ 4,853,703 $ 140,471 $ 2,826,098 $ 7,820,925 Common stock Additional Accumulated Retained Total Number of Stated (In thousands, except share and per share data) Balance, September 30, 2019 119,338,925 $ 597 $ 3,712,194 $ (114,583) $ 2,152,015 $ 5,750,223 Net income — — — — 178,673 178,673 Other comprehensive income — — — 1,052 — 1,052 Cash dividends ($0.575 per share) — — — — (69,557) (69,557) Common stock issued: Public and other stock offerings 2,758,929 13 263,259 — — 263,272 Stock-based compensation plans 164,549 1 4,111 — — 4,112 Balance, December 31, 2019 122,262,403 611 3,979,564 (113,531) 2,261,131 6,127,775 Net income — — — — 239,646 239,646 Other comprehensive income — — — 890 — 890 Cash dividends ($0.575 per share) — — — — (70,520) (70,520) Common stock issued: Public and other stock offerings 38,662 1 3,095 — — 3,096 Stock-based compensation plans 7,660 — 3,528 — — 3,528 Balance, March 31, 2020 122,308,725 $ 612 $ 3,986,187 $ (112,641) $ 2,430,257 $ 6,304,415 Shelf Registration, At-the-Market Equity Sales Program and Equity Issuances On February 11, 2020, we filed a shelf registration statement with the Securities and Exchange Commission (SEC) that allows us to issue up to $4.0 billion in common stock and/or debt securities, which expires February 11, 2023. At March 31, 2021, approximately $200 million of securities were available for issuance under the shelf registration statement. During the six months ended March 31, 2021, we executed forward sales under our ATM equity sales program with various forward sellers who borrowed and sold 2,472,912 shares of our common stock at an aggregate price of $238.6 million. During the six months ended March 31, 2021, we also settled forward sale agreements with respect to 4,537,669 shares that had been borrowed and sold by various forward sellers under the ATM program for net proceeds of $460.7 million. As of March 31, 2021, approximately $313 million of equity was available for issuance under the ATM program. Additionally, we had $115.6 million in available proceeds, based on a net price of $90.96 per share, from outstanding forward sale agreements, available through June 30, 2022. 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 as they are amortized. 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- Interest Rate Total (In thousands) September 30, 2020 $ 238 $ (57,827) $ (57,589) Other comprehensive income (loss) before reclassifications (129) 195,906 195,777 Amounts reclassified from accumulated other comprehensive income — 2,283 2,283 Net current-period other comprehensive income (loss) (129) 198,189 198,060 March 31, 2021 $ 109 $ 140,362 $ 140,471 Available- Interest Rate Total (In thousands) September 30, 2019 $ 132 $ (114,715) $ (114,583) Other comprehensive loss before reclassifications (163) — (163) Amounts reclassified from accumulated other comprehensive income (1) 2,106 2,105 Net current-period other comprehensive income (loss) (164) 2,106 1,942 March 31, 2020 $ (32) $ (112,609) $ (112,641)

Interim Pension and Other Postr

Interim Pension and Other Postretirement Benefit Plan Information	6 Months Ended
	Mar. 31, 2021
Retirement Benefits, Description [Abstract]
Interim Pension and Other Postretirement Benefit Plan Information	Interim Pension and Other Postretirement Benefit Plan InformationThe components of our net periodic pension cost for our pension and other postretirement benefit plans for the three and six months ended March 31, 2021 and 2020 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 Benefits Other Benefits 2021 2020 2021 2020 (In thousands) Components of net periodic pension cost: Service cost $ 4,613 $ 4,652 $ 4,306 $ 3,366 Interest cost (1) 5,028 5,843 2,660 2,653 Expected return on assets (1) (6,978) (7,079) (2,614) (2,625) Amortization of prior service cost (credit) (1) (58) (58) 43 43 Amortization of actuarial (gain) loss (1) 3,171 3,242 — (334) Net periodic pension cost $ 5,776 $ 6,600 $ 4,395 $ 3,103 Six Months Ended March 31 Pension Benefits Other Benefits 2021 2020 2021 2020 (In thousands) Components of net periodic pension cost: Service cost $ 9,225 $ 9,305 $ 8,612 $ 6,733 Interest cost (1) 10,056 11,686 5,320 5,306 Expected return on assets (1) (13,956) (14,158) (5,228) (5,249) Amortization of prior service cost (credit) (1) (116) (116) 86 87 Amortization of actuarial (gain) loss (1) 6,343 6,483 — (669) Net periodic pension cost $ 11,552 $ 13,200 $ 8,790 $ 6,208 (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, 2020. For the six months ended March 31, 2021 we contributed $8.7 million to our postretirement medical plans. We anticipate contributing a total of between $15 million and $25 million to our postretirement plans during fiscal 2021.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Mar. 31, 2021
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. We maintain liability insurance for various risks associated with the operation of our natural gas pipelines and facilities, including for property damage and bodily injury. These liability insurance policies generally require us to be responsible for the first $1.0 million (self-insured retention) of each incident. The National Transportation Safety Board (NTSB) held a public meeting on January 12, 2021 to determine the probable cause of the incident that occurred at a Dallas, Texas residence on February 23, 2018 that resulted in one fatality and injuries to four other residents. At the meeting, the Board deliberated and voted on proposed findings of fact, a probable cause statement, and safety recommendations. On February 8, 2021, the NTSB issued its final report that included an Executive Summary, Findings, Probable Cause, and Recommendations. Also on February 8, 2021, safety recommendations letters were distributed to recommendation recipients, including Atmos Energy. Following the release of the NTSB’s final report, the Railroad Commission of Texas (RRC) completed its safety evaluation related to the same incident finding four alleged violations and initiated an enforcement proceeding to pursue administrative penalties totaling $1.6 million. We are working with the RRC to resolve the alleged violations and satisfy the administrative penalties. 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 indexed to natural gas hubs. These purchase commitment contracts are detailed in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020. There were no material changes to the purchase commitments for the six months ended March 31, 2021. Rate Regulatory Proceedings As of March 31, 2021, 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, 2021.

Financial Instruments

Financial Instruments	6 Months Ended
	Mar. 31, 2021
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 14 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020. During the six months ended March 31, 2021, 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 2020-2021 heating season (generally October through March), in the jurisdictions where we are permitted to utilize financial instruments, we hedged approximately 39 percent, or 15.8 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. As of March 31, 2021, we had the following forward starting interest rate swaps to effectively fix the Treasury yield component which we designated as cash flow hedges at the time the agreements were executed: Planned Debt Issuance Date Amount Hedged Effective Interest Rate (In thousands) Fiscal 2022 $ 450,000 1.33 % Fiscal 2023 300,000 1.36 % Fiscal 2025 300,000 1.35 % $ 1,050,000 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, 2021, 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, 2021, we had 8,584 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, 2021 and September 30, 2020. The gross amounts of recognized assets and liabilities are netted within our unaudited condensed consolidated balance sheets to the extent that we have netting arrangements with our counterparties. However, for March 31, 2021 and September 30, 2020, no gross amounts and no cash collateral were netted within our consolidated balance sheet. Balance Sheet Location Assets Liabilities (In thousands) March 31, 2021 Designated As Hedges: Interest rate contracts Other current assets / $ 131,798 $ — Interest rate contracts Deferred charges and other assets / 193,786 — Total 325,584 — Not Designated As Hedges: Commodity contracts Other current assets / 1,574 (62) Total 1,574 (62) Gross / Net Financial Instruments $ 327,158 $ (62) Balance Sheet Location Assets Liabilities (In thousands) September 30, 2020 Designated As Hedges: Interest rate contracts Deferred charges and other assets / $ 73,055 $ — Total 73,055 — Not Designated As Hedges: Commodity contracts Other current assets / 5,687 (2,015) Commodity contracts Deferred charges and other assets / 1,936 — Total 7,623 (2,015) Gross / Net Financial Instruments $ 80,678 $ (2,015) 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 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, 2021 and 2020 was $1.5 million and $1.4 million and for the six months ended March 31, 2021 and 2020 was $2.9 million and $2.7 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, 2021 and 2020. The amounts included in the table below exclude gains and losses arising from ineffectiveness because those amounts are immediately recognized in the statement of comprehensive income as incurred. Three Months Ended March 31 Six Months Ended March 31 2021 2020 2021 2020 (In thousands) Increase in fair value: Interest rate agreements $ 136,864 $ — $ 195,906 $ — Recognition of losses in earnings due to settlements: Interest rate agreements 1,141 1,053 2,283 2,106 Total other comprehensive income (loss) from hedging, net of tax $ 138,005 $ 1,053 $ 198,189 $ 2,106 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, 2021, we had $112.2 million of net realized losses 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 losses 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 2049. 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 (In thousands) Next twelve months $ (4,566) Thereafter (107,653) Total $ (112,219) 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.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Mar. 31, 2021
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, accounts receivable and accounts payable 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, 2020. During the six months ended March 31, 2021, 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 9 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020. 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, 2021 and September 30, 2020. Assets and liabilities are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement. Quoted Significant Other Observable Inputs (Level 2) (1) Significant Netting and March 31, 2021 (In thousands) Assets: Financial instruments $ — $ 327,158 $ — $ — $ 327,158 Debt and equity securities Registered investment companies 34,501 — — — 34,501 Bond mutual funds 34,131 — — — 34,131 Bonds (2) — 35,755 — — 35,755 Money market funds — 5,105 — — 5,105 Total debt and equity securities 68,632 40,860 — — 109,492 Total assets $ 68,632 $ 368,018 $ — $ — $ 436,650 Liabilities: Financial instruments $ — $ 62 $ — $ — $ 62 Quoted Significant Other Observable Inputs (Level 2) (1) Significant Netting and September 30, 2020 (In thousands) Assets: Financial instruments $ — $ 80,678 $ — $ — $ 80,678 Debt and equity securities Registered investment companies 37,831 — — — 37,831 Bond mutual funds 29,166 — — — 29,166 Bonds (2) — 32,900 — — 32,900 Money market funds — 4,055 — — 4,055 Total debt and equity securities 66,997 36,955 — — 103,952 Total assets $ 66,997 $ 117,633 $ — $ — $ 184,630 Liabilities: Financial instruments $ — $ 2,015 $ — $ — $ 2,015 (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 further in Note 2 to the unaudited condensed consolidated financial statements, we adopted ASC 326 effective October 1, 2020. In accordance with the new guidance, 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, 2021, no allowance for credit losses was recorded for our available-for-sale debt securities. At March 31, 2021 and September 30, 2020, the amortized cost of our available-for-sale debt securities was $35.6 million and $32.6 million. At March 31, 2021, we maintained investments in bonds that have contractual maturity dates ranging from April 2021 through March 2024. 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, 2021 and September 30, 2020: March 31, 2021 September 30, 2020 (In thousands) Carrying Amount $ 7,360,000 $ 4,560,000 Fair Value $ 7,828,415 $ 5,597,183

Concentration of Credit Risk

Concentration of Credit Risk	6 Months Ended
	Mar. 31, 2021
Risks and Uncertainties [Abstract]
Concentration of Credit Risk	Concentration of Credit RiskInformation regarding our concentration of credit risk is disclosed in Note 16 to the consolidated financial statements in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020. During the six months ended March 31, 2021, there were no material changes in our concentration of credit risk.

Winter Storm Uri

Winter Storm Uri	6 Months Ended
	Mar. 31, 2021
Unusual or Infrequent Items, or Both [Abstract]
Winter Storm Uri	Winter Storm Uri Overview A historic winter storm impacted supply, market pricing and demand for natural gas in our service territories in mid-February. During this time, the governors of Kansas and Texas each declared a state of emergency, and certain regulatory agencies issued emergency orders that impacted the utility and natural gas industries, including statewide utilities curtailment programs and orders encouraging or requiring jurisdictional natural gas utilities to work to ensure customers were provided with safe and reliable natural gas service. Due to the historic nature of this winter storm, we experienced unforeseeable and unprecedented market pricing for gas costs, which resulted in aggregated natural gas purchases during the month of February of approximately $2.3 billion. These gas costs were paid by the end of March 2021. Incremental Financing As discussed in Note 6 to the unaudited condensed consolidated financial statements, on March 9, 2021, we completed a public offering of $2.2 billion in debt securities and the net proceeds from the offering, after the underwriting discount and offering expenses, were used to substantially fund these purchased gas costs. As a result of this unplanned debt issuance, S&P lowered its long-term/short-term credit ratings from A/A-1 to A-/A-2 and placed our ratings under negative outlook. Moody’s reaffirmed its long-term and short-term credit ratings and placed our ratings under negative outlook. These credit rating adjustments and the issuance of unplanned debt did not impact our ability to satisfy our debt covenants. Regulatory Asset Accounting Our purchased gas costs are recoverable through purchased gas cost adjustment mechanisms in each state where we operate. Due to the unprecedented level of purchased gas costs incurred during Winter Storm Uri, the Kansas Corporation Commission (KCC) and the Railroad Commission of Texas (RRC) issued orders authorizing natural gas utilities to record a regulatory asset to account for the extraordinary costs associated with the winter storm. Pursuant to these orders, as of March 31, 2021, we have recorded a $2.1 billion regulatory asset for incremental costs, including carrying costs, incurred in Kansas ($76.7 million) and Texas ($2,016.8 million) within deferred charges and other assets on our condensed consolidated balance sheet. These costs are subject to review for prudency by each commission and may be adjusted. Income Taxes We deduct our purchased gas costs for federal income tax purposes in the period they are paid. Based on our current projection of taxable income for fiscal 2021 and the expected magnitude of the purchased gas cost deduction, we recorded a $469.4 million (tax effected) increase in our net operating loss carryforwards and a corresponding increase to our deferred tax liability as of March 31, 2021. At March 31, 2021, we had $813.1 million (tax effected) of federal net operating loss carryforwards. The federal net operating loss carryforwards are available to offset future taxable income. Net operating loss carryforwards incurred prior to December 22, 2017 begin to expire in 2029. The Company also has $57.5 million (tax effected) of state net operating loss carryforwards (net of $15.3 million of federal effects) and $1.8 million of state tax credits carryforwards (net of $0.5 million of federal effects). Depending on the jurisdiction in which the state net operating loss was generated, the carryforwards are subject to expiration through the remainder of fiscal 2021. Securitization Legislation To minimize the impact on the customer bill by extending the recovery periods for these unprecedented purchased gas costs, the Kansas and Texas State Legislatures each introduced securitization legislation during our fiscal second quarter. The following summarizes the status of the legislation as of the date of this filing. Kansas The Kansas securitization legislation permits a natural gas public utility, in its sole discretion, to apply to the KCC for a financing order for the recovery of qualified extraordinary costs through the issuance of bonds. Within 25 days after a complete application is filed, the KCC shall establish a procedural schedule that requires it to issue a decision on the application within 180 days from the date a complete application was filed. Utilities may apply for a recovery period of up to 32 years. The legislation became effective April 9, 2021. Texas The proposed Texas securitization legislation authorizes the RRC to issue a statewide securitization financing order to recover the extraordinary gas costs incurred by natural gas utilities from current and future customers through uniform monthly volumetric charges for a period of up to 30 years. The proposed legislation provides that natural gas utilities have 60 days from the passage of the bill to submit extraordinary gas costs incurred during Winter Storm Uri for a prudency review. The RRC has 90 days to approve each filing. Following the approval of all applications, the RRC will issue a financing order to the Texas Public Financing Authority authorizing the issuance of customer rate relief bonds to securitize the aggregated extraordinary costs for all participating utilities. The participating utilities, as servicers acting on behalf of the state of the securitization financing, will bill and collect customer rate relief charges from their current and future customers and remit the collections to the state issuer of the securitization financing. The proposed legislation is still being considered by the Texas Legislature.

Unaudited Financial Informati_2

Unaudited Financial Information (Policies)	6 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Accounting pronouncements adopted and not yet adopted	Accounting pronouncements adopted in fiscal 2021 Effective October 1, 2020, we adopted new accounting guidance that requires credit losses on most financial assets measured at amortized cost and certain other instruments to be measured using an expected credit loss model. Under this model, we estimate credit losses over the entire contractual term of the instrument from the date of initial recognition of that instrument. The new guidance also introduces a new impairment recognition model for available-for-sale debt securities that will require credit losses to be recorded through an allowance account. We adopted the new guidance using a modified retrospective method. The adoption of this standard did not have a material impact on our financial position, results of operations and cash flows and no adjustments were made to October 1, 2020 opening balances as a result of this adoption. As required under the modified retrospective method of adoption, results for the reporting period beginning after October 1, 2020 are presented under Accounting Standards Codification (ASC) 326, while prior period amounts are not adjusted. See Notes 5 and 12 to the unaudited condensed consolidated financial statements for further discussion of implementation of the standard. Accounting pronouncements that will be effective after fiscal 2021 In March 2020, the Financial Accounting Standards Board (FASB) issued optional guidance which will ease the potential burden in accounting for or recognizing the effects of reference rate reform on financial reporting. The amendments provide optional expedients and exceptions for applying U.S. GAAP to contracts, hedging relationships and other transactions affected
Regulatory assets and liabilities	Regulatory assets and liabilities 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 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.
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 7 to the unaudited condensed consolidated financial statements, when the impact is dilutive.
Fair value measurement	Fair Value MeasurementsWe 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, accounts receivable and accounts payable 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, 2020. During the six months ended March 31, 2021, there were no changes in these methods.

Unaudited Financial Informati_3

Unaudited Financial Information (Table)	6 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Schedule of Regulatory Assets	Significant regulatory assets and liabilities as of March 31, 2021 and September 30, 2020 included the following: March 31, September 30, (In thousands) Regulatory assets: Pension and postretirement benefit costs $ 143,685 $ 149,089 Infrastructure mechanisms (1) 189,154 183,943 Winter Storm Uri incremental costs (2) 2,093,534 — Deferred gas costs 19,636 40,593 Recoverable loss on reacquired debt 4,165 4,894 Deferred pipeline record collection costs 30,415 29,839 Other 6,093 6,283 $ 2,486,682 $ 414,641 Regulatory liabilities: Regulatory excess deferred taxes (3) $ 702,393 $ 718,651 Regulatory cost of removal obligation 531,625 531,096 Deferred gas costs 122,864 19,985 Asset retirement obligation 20,348 20,348 APT annual adjustment mechanism 44,291 57,379 Other 25,828 19,554 $ 1,447,349 $ 1,367,013 (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) Includes extraordinary gas costs incurred during Winter Storm Uri and related carrying costs. See Note 8 to the unaudited condensed consolidated financial statements for further information. This amount is recorded within deferred charges and other assets on the condensed consolidated balance sheet as of March 31, 2021. (3) Includes amount from the remeasurement of the net deferred tax liability included in our rate base as a result of the Tax Cuts and Jobs Act of 2017 (the "TCJA") and a Kansas legislative change enacted in fiscal 2020. Of this amount, $62.9 million as of March 31, 2021 and $20.9 million as of September 30, 2020 is recorded in other current liabilities. These liabilities are currently being returned to customers in most of our jurisdictions on a provisional basis over 15 to 69 years until formal orders establish the final refund periods. During the six months ended March 31, 2021, our effective income tax rate decreased from 22.1% to 19.8%, primarily due to the approval of the amortization of excess deferred income taxes to APT customers.
Schedule of Regulatory Liabilities	Significant regulatory assets and liabilities as of March 31, 2021 and September 30, 2020 included the following: March 31, September 30, (In thousands) Regulatory assets: Pension and postretirement benefit costs $ 143,685 $ 149,089 Infrastructure mechanisms (1) 189,154 183,943 Winter Storm Uri incremental costs (2) 2,093,534 — Deferred gas costs 19,636 40,593 Recoverable loss on reacquired debt 4,165 4,894 Deferred pipeline record collection costs 30,415 29,839 Other 6,093 6,283 $ 2,486,682 $ 414,641 Regulatory liabilities: Regulatory excess deferred taxes (3) $ 702,393 $ 718,651 Regulatory cost of removal obligation 531,625 531,096 Deferred gas costs 122,864 19,985 Asset retirement obligation 20,348 20,348 APT annual adjustment mechanism 44,291 57,379 Other 25,828 19,554 $ 1,447,349 $ 1,367,013 (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) Includes extraordinary gas costs incurred during Winter Storm Uri and related carrying costs. See Note 8 to the unaudited condensed consolidated financial statements for further information. This amount is recorded within deferred charges and other assets on the condensed consolidated balance sheet as of March 31, 2021. (3) Includes amount from the remeasurement of the net deferred tax liability included in our rate base as a result of the Tax Cuts and Jobs Act of 2017 (the "TCJA") and a Kansas legislative change enacted in fiscal 2020. Of this amount, $62.9 million as of March 31, 2021 and $20.9 million as of September 30, 2020 is recorded in other current liabilities. These liabilities are currently being returned to customers in most of our jurisdictions on a provisional basis over 15 to 69 years until formal orders establish the final refund periods. During the six months ended March 31, 2021, our effective income tax rate decreased from 22.1% to 19.8%, primarily due to the approval of the amortization of excess deferred income taxes to APT customers.

Segment Information (Table)

Segment Information (Table)	6 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Income statements and capital expenditures for the three and six months ended March 31, 2021 and 2020 by segment are presented in the following tables: Three Months Ended March 31, 2021 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Operating revenues from external parties $ 1,281,826 $ 37,247 $ — $ 1,319,073 Intersegment revenues 848 116,921 (117,769) — Total operating revenues 1,282,674 154,168 (117,769) 1,319,073 Purchased gas cost 691,147 113 (117,451) 573,809 Operation and maintenance expense 123,990 32,703 (318) 156,375 Depreciation and amortization expense 85,667 32,969 — 118,636 Taxes, other than income 78,615 9,834 — 88,449 Operating income 303,255 78,549 — 381,804 Other non-operating income (expense) (760) 3,594 — 2,834 Interest charges 14,017 12,079 — 26,096 Income before income taxes 288,478 70,064 — 358,542 Income tax expense 56,142 5,646 — 61,788 Net income $ 232,336 $ 64,418 $ — $ 296,754 Capital expenditures $ 296,184 $ 92,735 $ — $ 388,919 Three Months Ended March 31, 2020 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Operating revenues from external parties $ 932,296 $ 45,369 $ — $ 977,665 Intersegment revenues 709 100,868 (101,577) — Total operating revenues 933,005 146,237 (101,577) 977,665 Purchased gas cost 418,935 202 (101,254) 317,883 Operation and maintenance expense 115,851 32,296 (323) 147,824 Depreciation and amortization expense 76,265 29,651 — 105,916 Taxes, other than income 68,413 6,191 — 74,604 Operating income 253,541 77,897 — 331,438 Other non-operating income (expense) (5,191) 2,202 — (2,989) Interest charges 10,797 11,374 — 22,171 Income before income taxes 237,553 68,725 — 306,278 Income tax expense 50,489 16,143 — 66,632 Net income $ 187,064 $ 52,582 $ — $ 239,646 Capital expenditures $ 373,313 $ 92,238 $ — $ 465,551 Six Months Ended March 31, 2021 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Operating revenues from external parties $ 2,157,713 $ 75,840 $ — $ 2,233,553 Intersegment revenues 1,611 238,041 (239,652) — Total operating revenues 2,159,324 313,881 (239,652) 2,233,553 Purchased gas cost 1,102,219 (1,131) (239,019) 862,069 Operation and maintenance expense 232,792 62,859 (633) 295,018 Depreciation and amortization expense 168,537 65,384 — 233,921 Taxes, other than income 142,967 18,934 — 161,901 Operating income 512,809 167,835 — 680,644 Other non-operating income 75 8,831 — 8,906 Interest charges 24,729 23,377 — 48,106 Income before income taxes 488,155 153,289 — 641,444 Income tax expense 102,127 24,885 — 127,012 Net income $ 386,028 $ 128,404 $ — $ 514,432 Capital expenditures $ 602,200 $ 243,528 $ — $ 845,728 Six Months Ended March 31, 2020 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Operating revenues from external parties $ 1,760,136 $ 93,092 $ — $ 1,853,228 Intersegment revenues 1,373 201,321 (202,694) — Total operating revenues 1,761,509 294,413 (202,694) 1,853,228 Purchased gas cost 816,493 301 (202,043) 614,751 Operation and maintenance expense 230,203 70,517 (651) 300,069 Depreciation and amortization expense 152,339 58,639 — 210,978 Taxes, other than income 128,656 14,555 — 143,211 Operating income 433,818 150,401 — 584,219 Other non-operating income (expense) (3,237) 5,135 — 1,898 Interest charges 27,159 22,241 — 49,400 Income before income taxes 403,422 133,295 — 536,717 Income tax expense 86,601 31,797 — 118,398 Net income $ 316,821 $ 101,498 $ — $ 418,319 Capital expenditures $ 777,560 $ 217,177 $ — $ 994,737 Balance sheet information at March 31, 2021 and September 30, 2020 by segment is presented in the following tables: March 31, 2021 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Property, plant and equipment, net $ 10,465,072 $ 3,574,516 $ — $ 14,039,588 Total assets $ 18,661,545 $ 3,799,037 $ (3,051,772) $ 19,408,810 September 30, 2020 Distribution Pipeline and Storage Eliminations Consolidated (In thousands) Property, plant and equipment, net $ 9,944,978 $ 3,410,369 $ — $ 13,355,347 Total assets $ 14,578,176 $ 3,647,907 $ (2,867,051) $ 15,359,032

Earnings Per Share (Table)

Earnings Per Share (Table)	6 Months Ended
	Mar. 31, 2021
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, 2021 and 2020 are calculated as follows: Three Months Ended March 31 Six Months Ended March 31 2021 2020 2021 2020 (In thousands, except per share amounts) Basic Earnings Per Share Net income $ 296,754 $ 239,646 $ 514,432 $ 418,319 Less: Income allocated to participating securities 199 178 350 314 Income available to common shareholders $ 296,555 $ 239,468 $ 514,082 $ 418,005 Basic weighted average shares outstanding 129,161 122,916 128,098 122,015 Net income per share — Basic $ 2.30 $ 1.95 $ 4.01 $ 3.43 Diluted Earnings Per Share Income available to common shareholders $ 296,555 $ 239,468 $ 514,082 $ 418,005 Effect of dilutive shares — — — — Income available to common shareholders $ 296,555 $ 239,468 $ 514,082 $ 418,005 Basic weighted average shares outstanding 129,161 122,916 128,098 122,015 Dilutive shares 3 81 2 164 Diluted weighted average shares outstanding 129,164 122,997 128,100 122,179 Net income per share - Diluted $ 2.30 $ 1.95 $ 4.01 $ 3.42

Revenue and Accounts Receivab_2

Revenue and Accounts Receivable (Table)	6 Months Ended
	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
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, 2021 and 2020. Three Months Ended March 31, 2021 Three Months Ended March 31, 2020 Distribution Pipeline and Storage Distribution Pipeline and Storage (In thousands) Gas sales revenues: Residential $ 893,720 $ — $ 596,315 $ — Commercial 326,182 — 230,779 — Industrial 31,066 — 25,628 — Public authority and other 20,227 — 14,662 — Total gas sales revenues 1,271,195 — 867,384 — Transportation revenues 30,973 151,565 28,504 154,748 Miscellaneous revenues 3,325 3,878 6,986 1,335 Revenues from contracts with customers 1,305,493 155,443 902,874 156,083 Alternative revenue program revenues (1) (23,313) (1,275) 29,638 (9,846) Other revenues 494 — 493 — Total operating revenues $ 1,282,674 $ 154,168 $ 933,005 $ 146,237 Six Months Ended March 31, 2021 Six Months Ended March 31, 2020 Distribution Pipeline and Storage Distribution Pipeline and Storage (In thousands) Gas sales revenues: Residential $ 1,485,554 $ — $ 1,148,391 $ — Commercial 535,129 — 442,093 — Industrial 55,774 — 50,553 — Public authority and other 33,289 — 27,684 — Total gas sales revenues 2,109,746 — 1,668,721 — Transportation revenues 58,740 316,326 55,144 306,758 Miscellaneous revenues 5,721 9,026 13,772 6,490 Revenues from contracts with customers 2,174,207 325,352 1,737,637 313,248 Alternative revenue program revenues (1) (15,872) (11,471) 22,887 (18,835) Other revenues 989 — 985 — Total operating revenues $ 2,159,324 $ 313,881 $ 1,761,509 $ 294,413 (1) In our distribution segment, we have weather-normalization adjustment mechanisms that serve to mitigate the effects of weather on our revenue. Additionally, 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 regulatorily determined revenue benchmark.
Allowance for Credit Loss Activity	Rollforwards of our allowance for uncollectible accounts for the three and six months ended March 31, 2021 are presented in the table below. The allowance excludes the gas cost portion of customers’ bills for approximately 78 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. Three Months Ended March 31, 2021 (In thousands) Beginning balance, December 31, 2020 $ 35,089 Current period provisions 11,532 Write-offs charged against allowance (2,381) Recoveries of amounts previously written off 440 Ending balance, March 31, 2021 $ 44,680 Six Months Ended March 31, 2021 (In thousands) Beginning balance, September 30, 2020 $ 29,949 Current period provisions 18,469 Write-offs charged against allowance (4,669) Recoveries of amounts previously written off 931 Ending balance, March 31, 2021 $ 44,680

Debt (Table)

Debt (Table)	6 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	Long-term debt at March 31, 2021 and September 30, 2020 consisted of the following: March 31, 2021 September 30, 2020 (In thousands) Unsecured 0.625% Senior Notes, due 2023 $ 1,100,000 $ — Unsecured 3.00% Senior Notes, due 2027 500,000 500,000 Unsecured 2.625% Senior Notes, due 2029 300,000 300,000 Unsecured 1.50% Senior Notes, due 2031 600,000 — Unsecured 5.95% Senior Notes, due 2034 200,000 200,000 Unsecured 5.50% Senior Notes, due 2041 400,000 400,000 Unsecured 4.15% Senior Notes, due 2043 500,000 500,000 Unsecured 4.125% Senior Notes, due 2044 750,000 750,000 Unsecured 4.30% Senior Notes, due 2048 600,000 600,000 Unsecured 4.125% Senior Notes, due 2049 450,000 450,000 Unsecured 3.375% Senior Notes, due 2049 500,000 500,000 Floating-rate term loan, due April 2022 200,000 200,000 Floating-rate Senior Notes, due 2023 1,100,000 — Medium-term note Series A, 1995-1, 6.67%, due 2025 10,000 10,000 Unsecured 6.75% Debentures, due 2028 150,000 150,000 Finance lease obligations 8,612 8,631 Total long-term debt 7,368,612 4,568,631 Less: Original issue discount on unsecured senior notes and debentures 3,030 583 Debt issuance cost 49,001 36,104 Current maturities 177 165 $ 7,316,404 $ 4,531,779

Shareholders' Equity (Table)

Shareholders' Equity (Table)	6 Months Ended
	Mar. 31, 2021
Equity [Abstract]
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, 2021 and 2020. Common stock Additional Accumulated Retained Total Number of Stated (In thousands, except share and per share data) Balance, September 30, 2020 125,882,477 $ 629 $ 4,377,149 $ (57,589) $ 2,471,014 $ 6,791,203 Net income — — — — 217,678 217,678 Other comprehensive income — — — 60,121 — 60,121 Cash dividends ($0.625 per share) — — — — (79,023) (79,023) Common stock issued: Public and other stock offerings 2,126,118 11 219,998 — — 220,009 Stock-based compensation plans 144,366 1 3,167 — — 3,168 Balance, December 31, 2020 128,152,961 641 4,600,314 2,532 2,609,669 7,213,156 Net income — — — — 296,754 296,754 Other comprehensive income — — — 137,939 — 137,939 Cash dividends ($0.625 per share) — — — — (80,325) (80,325) Common stock issued: Public and other stock offerings 2,498,026 12 248,948 — — 248,960 Stock-based compensation plans 16,122 — 4,441 — — 4,441 Balance, March 31, 2021 130,667,109 $ 653 $ 4,853,703 $ 140,471 $ 2,826,098 $ 7,820,925 Common stock Additional Accumulated Retained Total Number of Stated (In thousands, except share and per share data) Balance, September 30, 2019 119,338,925 $ 597 $ 3,712,194 $ (114,583) $ 2,152,015 $ 5,750,223 Net income — — — — 178,673 178,673 Other comprehensive income — — — 1,052 — 1,052 Cash dividends ($0.575 per share) — — — — (69,557) (69,557) Common stock issued: Public and other stock offerings 2,758,929 13 263,259 — — 263,272 Stock-based compensation plans 164,549 1 4,111 — — 4,112 Balance, December 31, 2019 122,262,403 611 3,979,564 (113,531) 2,261,131 6,127,775 Net income — — — — 239,646 239,646 Other comprehensive income — — — 890 — 890 Cash dividends ($0.575 per share) — — — — (70,520) (70,520) Common stock issued: Public and other stock offerings 38,662 1 3,095 — — 3,096 Stock-based compensation plans 7,660 — 3,528 — — 3,528 Balance, March 31, 2020 122,308,725 $ 612 $ 3,986,187 $ (112,641) $ 2,430,257 $ 6,304,415
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- Interest Rate Total (In thousands) September 30, 2020 $ 238 $ (57,827) $ (57,589) Other comprehensive income (loss) before reclassifications (129) 195,906 195,777 Amounts reclassified from accumulated other comprehensive income — 2,283 2,283 Net current-period other comprehensive income (loss) (129) 198,189 198,060 March 31, 2021 $ 109 $ 140,362 $ 140,471 Available- Interest Rate Total (In thousands) September 30, 2019 $ 132 $ (114,715) $ (114,583) Other comprehensive loss before reclassifications (163) — (163) Amounts reclassified from accumulated other comprehensive income (1) 2,106 2,105 Net current-period other comprehensive income (loss) (164) 2,106 1,942 March 31, 2020 $ (32) $ (112,609) $ (112,641)

Interim Pension and Other Pos_2

Interim Pension and Other Postretirement Benefit Plan Information (Table)	6 Months Ended
	Mar. 31, 2021
Retirement Benefits, Description [Abstract]
Schedule of Net Benefit Costs	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, 2021 and 2020 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 Benefits Other Benefits 2021 2020 2021 2020 (In thousands) Components of net periodic pension cost: Service cost $ 4,613 $ 4,652 $ 4,306 $ 3,366 Interest cost (1) 5,028 5,843 2,660 2,653 Expected return on assets (1) (6,978) (7,079) (2,614) (2,625) Amortization of prior service cost (credit) (1) (58) (58) 43 43 Amortization of actuarial (gain) loss (1) 3,171 3,242 — (334) Net periodic pension cost $ 5,776 $ 6,600 $ 4,395 $ 3,103 Six Months Ended March 31 Pension Benefits Other Benefits 2021 2020 2021 2020 (In thousands) Components of net periodic pension cost: Service cost $ 9,225 $ 9,305 $ 8,612 $ 6,733 Interest cost (1) 10,056 11,686 5,320 5,306 Expected return on assets (1) (13,956) (14,158) (5,228) (5,249) Amortization of prior service cost (credit) (1) (116) (116) 86 87 Amortization of actuarial (gain) loss (1) 6,343 6,483 — (669) Net periodic pension cost $ 11,552 $ 13,200 $ 8,790 $ 6,208 (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, 2020.

Financial Instruments (Table)

Financial Instruments (Table)	6 Months Ended
	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivatives	As of March 31, 2021, we had the following forward starting interest rate swaps to effectively fix the Treasury yield component which we designated as cash flow hedges at the time the agreements were executed: Planned Debt Issuance Date Amount Hedged Effective Interest Rate (In thousands) Fiscal 2022 $ 450,000 1.33 % Fiscal 2023 300,000 1.36 % Fiscal 2025 300,000 1.35 % $ 1,050,000
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, 2021 and September 30, 2020. The gross amounts of recognized assets and liabilities are netted within our unaudited condensed consolidated balance sheets to the extent that we have netting arrangements with our counterparties. However, for March 31, 2021 and September 30, 2020, no gross amounts and no cash collateral were netted within our consolidated balance sheet. Balance Sheet Location Assets Liabilities (In thousands) March 31, 2021 Designated As Hedges: Interest rate contracts Other current assets / $ 131,798 $ — Interest rate contracts Deferred charges and other assets / 193,786 — Total 325,584 — Not Designated As Hedges: Commodity contracts Other current assets / 1,574 (62) Total 1,574 (62) Gross / Net Financial Instruments $ 327,158 $ (62) Balance Sheet Location Assets Liabilities (In thousands) September 30, 2020 Designated As Hedges: Interest rate contracts Deferred charges and other assets / $ 73,055 $ — Total 73,055 — Not Designated As Hedges: Commodity contracts Other current assets / 5,687 (2,015) Commodity contracts Deferred charges and other assets / 1,936 — Total 7,623 (2,015) Gross / Net Financial Instruments $ 80,678 $ (2,015)
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, 2021 and 2020. The amounts included in the table below exclude gains and losses arising from ineffectiveness because those amounts are immediately recognized in the statement of comprehensive income as incurred. Three Months Ended March 31 Six Months Ended March 31 2021 2020 2021 2020 (In thousands) Increase in fair value: Interest rate agreements $ 136,864 $ — $ 195,906 $ — Recognition of losses in earnings due to settlements: Interest rate agreements 1,141 1,053 2,283 2,106 Total other comprehensive income (loss) from hedging, net of tax $ 138,005 $ 1,053 $ 198,189 $ 2,106
Schedule Of Expected Deferred Gains (Losses) Recognition	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 (In thousands) Next twelve months $ (4,566) Thereafter (107,653) Total $ (112,219)

Fair Value Measurements (Table)

Fair Value Measurements (Table)	6 Months Ended
	Mar. 31, 2021
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, 2021 and September 30, 2020. Assets and liabilities are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement. Quoted Significant Other Observable Inputs (Level 2) (1) Significant Netting and March 31, 2021 (In thousands) Assets: Financial instruments $ — $ 327,158 $ — $ — $ 327,158 Debt and equity securities Registered investment companies 34,501 — — — 34,501 Bond mutual funds 34,131 — — — 34,131 Bonds (2) — 35,755 — — 35,755 Money market funds — 5,105 — — 5,105 Total debt and equity securities 68,632 40,860 — — 109,492 Total assets $ 68,632 $ 368,018 $ — $ — $ 436,650 Liabilities: Financial instruments $ — $ 62 $ — $ — $ 62 Quoted Significant Other Observable Inputs (Level 2) (1) Significant Netting and September 30, 2020 (In thousands) Assets: Financial instruments $ — $ 80,678 $ — $ — $ 80,678 Debt and equity securities Registered investment companies 37,831 — — — 37,831 Bond mutual funds 29,166 — — — 29,166 Bonds (2) — 32,900 — — 32,900 Money market funds — 4,055 — — 4,055 Total debt and equity securities 66,997 36,955 — — 103,952 Total assets $ 66,997 $ 117,633 $ — $ — $ 184,630 Liabilities: Financial instruments $ — $ 2,015 $ — $ — $ 2,015 (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, 2021 and September 30, 2020: March 31, 2021 September 30, 2020 (In thousands) Carrying Amount $ 7,360,000 $ 4,560,000 Fair Value $ 7,828,415 $ 5,597,183

Nature of Business (Details)

Nature of Business (Details) customer in Millions	Mar. 31, 2021statecustomerregulated_distribution_division
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of customers serviced | customer	3
Number of regulated distribution divisions | regulated_distribution_division	6
Number of states with service areas | state	8

Unaudited Financial Informati_4

Unaudited Financial Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Regulatory Asset [Line Items]
Regulatory assets	$ 2,486,682		$ 414,641
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 1,447,349		1,367,013
Effective income tax rate	19.80%	22.10%
Regulatory excess deferred taxes
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 702,393		718,651
Regulatory excess deferred taxes | Other Current Liabilities
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 62,900		20,900
Regulatory excess deferred taxes | Other Current Liabilities | Minimum
Regulatory Liabilities [Line Items]
Return basis, term	15 years
Regulatory excess deferred taxes | Other Current Liabilities | Maximum
Regulatory Liabilities [Line Items]
Return basis, term	69 years
Regulatory cost of removal obligation
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 531,625		531,096
Deferred gas costs
Regulatory Liabilities [Line Items]
Regulatory liabilities	122,864		19,985
Asset retirement obligation
Regulatory Liabilities [Line Items]
Regulatory liabilities	20,348		20,348
APT annual adjustment mechanism
Regulatory Liabilities [Line Items]
Regulatory liabilities	44,291		57,379
Other
Regulatory Liabilities [Line Items]
Regulatory liabilities	25,828		19,554
Pension and postretirement benefit costs
Regulatory Asset [Line Items]
Regulatory assets	143,685		149,089
Infrastructure mechanisms
Regulatory Asset [Line Items]
Regulatory assets	189,154		183,943
Winter Storm Uri incremental costs
Regulatory Asset [Line Items]
Regulatory assets	2,093,534		0
Deferred gas costs
Regulatory Asset [Line Items]
Regulatory assets	19,636		40,593
Recoverable loss on reacquired debt
Regulatory Asset [Line Items]
Regulatory assets	4,165		4,894
Deferred pipeline record collection costs
Regulatory Asset [Line Items]
Regulatory assets	30,415		29,839
Other
Regulatory Asset [Line Items]
Regulatory assets	$ 6,093		$ 6,283

Segment Information (Details)

Segment Information (Details) $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2021USD ($)state	Dec. 31, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Mar. 31, 2021USD ($)state	Mar. 31, 2020USD ($)	Sep. 30, 2020USD ($)
Segment Reporting Information [Line Items]
Number of states with service areas | state	8				8
Segment Reporting Information Profit Loss [Abstract]
Operating revenues	$ 1,319,073		$ 977,665		$ 2,233,553	$ 1,853,228
Purchased gas cost	573,809		317,883		862,069	614,751
Operation and maintenance expense	156,375		147,824		295,018	300,069
Depreciation and amortization expense	118,636		105,916		233,921	210,978
Taxes, other than income	88,449		74,604		161,901	143,211
Operating income	381,804		331,438		680,644	584,219
Other non-operating income (expense)	2,834		(2,989)		8,906	1,898
Interest charges	26,096		22,171		48,106	49,400
Income before income taxes	358,542		306,278		641,444	536,717
Income tax (benefit) expense	61,788		66,632		127,012	118,398
Net income	296,754	$ 217,678	239,646	$ 178,673	514,432	418,319
Capital expenditures	388,919		465,551		845,728	994,737
Segment Reporting Information, Balance Sheet [Abstract]
Property, plant and equipment, net	14,039,588				14,039,588		$ 13,355,347
Total assets	19,408,810				19,408,810		15,359,032
Distribution
Segment Reporting Information Profit Loss [Abstract]
Operating revenues	1,281,826		932,296		2,157,713	1,760,136
Pipeline and Storage
Segment Reporting Information Profit Loss [Abstract]
Operating revenues	37,247		45,369		75,840	93,092
Operating Segments | Distribution
Segment Reporting Information Profit Loss [Abstract]
Operating revenues	1,282,674		933,005		2,159,324	1,761,509
Purchased gas cost	691,147		418,935		1,102,219	816,493
Operation and maintenance expense	123,990		115,851		232,792	230,203
Depreciation and amortization expense	85,667		76,265		168,537	152,339
Taxes, other than income	78,615		68,413		142,967	128,656
Operating income	303,255		253,541		512,809	433,818
Other non-operating income (expense)	(760)		(5,191)		75	(3,237)
Interest charges	14,017		10,797		24,729	27,159
Income before income taxes	288,478		237,553		488,155	403,422
Income tax (benefit) expense	56,142		50,489		102,127	86,601
Net income	232,336		187,064		386,028	316,821
Capital expenditures	296,184		373,313		602,200	777,560
Segment Reporting Information, Balance Sheet [Abstract]
Property, plant and equipment, net	10,465,072				10,465,072		9,944,978
Total assets	18,661,545				18,661,545		14,578,176
Operating Segments | Pipeline and Storage
Segment Reporting Information Profit Loss [Abstract]
Operating revenues	154,168		146,237		313,881	294,413
Purchased gas cost	113		202		(1,131)	301
Operation and maintenance expense	32,703		32,296		62,859	70,517
Depreciation and amortization expense	32,969		29,651		65,384	58,639
Taxes, other than income	9,834		6,191		18,934	14,555
Operating income	78,549		77,897		167,835	150,401
Other non-operating income (expense)	3,594		2,202		8,831	5,135
Interest charges	12,079		11,374		23,377	22,241
Income before income taxes	70,064		68,725		153,289	133,295
Income tax (benefit) expense	5,646		16,143		24,885	31,797
Net income	64,418		52,582		128,404	101,498
Capital expenditures	92,735		92,238		243,528	217,177
Segment Reporting Information, Balance Sheet [Abstract]
Property, plant and equipment, net	3,574,516				3,574,516		3,410,369
Total assets	3,799,037				3,799,037		3,647,907
Eliminations
Segment Reporting Information Profit Loss [Abstract]
Operating revenues	(117,769)		(101,577)		(239,652)	(202,694)
Purchased gas cost	(117,451)		(101,254)		(239,019)	(202,043)
Operation and maintenance expense	(318)		(323)		(633)	(651)
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 (benefit) expense	0		0		0	0
Net income	0		0		0	0
Capital expenditures	0		0		0	0
Segment Reporting Information, Balance Sheet [Abstract]
Property, plant and equipment, net	0				0		0
Total assets	(3,051,772)				(3,051,772)		$ (2,867,051)
Eliminations | Distribution
Segment Reporting Information Profit Loss [Abstract]
Operating revenues	848		709		1,611	1,373
Eliminations | Pipeline and Storage
Segment Reporting Information Profit Loss [Abstract]
Operating revenues	$ 116,921		$ 100,868		$ 238,041	$ 201,321

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2021	Mar. 31, 2020
Basic Earnings Per Share
Net income	$ 296,754	$ 217,678	$ 239,646	$ 178,673	$ 514,432	$ 418,319
Less: Income allocated to participating securities	199		178		350	314
Income available to common shareholders	$ 296,555		$ 239,468		$ 514,082	$ 418,005
Basic weighted average shares outstanding (in shares)	129,161		122,916		128,098	122,015
Net income per share - Basic (USD per share)	$ 2.30		$ 1.95		$ 4.01	$ 3.43
Diluted Earnings Per Share
Income available to common shareholders	$ 296,555		$ 239,468		$ 514,082	$ 418,005
Effect of dilutive shares	0		0		0	0
Income available to common shareholders	$ 296,555		$ 239,468		$ 514,082	$ 418,005
Basic weighted average shares outstanding (in shares)	129,161		122,916		128,098	122,015
Dilutive shares (in shares)	3		81		2	164
Diluted weighted average shares outstanding (in shares)	129,164		122,997		128,100	122,179
Net income per share - Diluted (USD per share)	$ 2.30		$ 1.95		$ 4.01	$ 3.42

Revenue and Accounts Receivab_3

Revenue and Accounts Receivable - Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,319,073	$ 977,665	$ 2,233,553	$ 1,853,228
Distribution
Disaggregation of Revenue [Line Items]
Total operating revenues	1,281,826	932,296	$ 2,157,713	1,760,136
Regulatory mechanism threshold (in percent)			75.00%
Pipeline and Storage
Disaggregation of Revenue [Line Items]
Total operating revenues	37,247	45,369	$ 75,840	93,092
Operating Segments | Distribution
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,305,493	902,874	2,174,207	1,737,637
Alternative revenue program revenues	(23,313)	29,638	(15,872)	22,887
Other revenues	494	493	989	985
Total operating revenues	1,282,674	933,005	2,159,324	1,761,509
Operating Segments | Distribution | Gas sales revenues:
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,271,195	867,384	2,109,746	1,668,721
Operating Segments | Distribution | Gas sales revenues: | Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	893,720	596,315	1,485,554	1,148,391
Operating Segments | Distribution | Gas sales revenues: | Commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	326,182	230,779	535,129	442,093
Operating Segments | Distribution | Gas sales revenues: | Industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	31,066	25,628	55,774	50,553
Operating Segments | Distribution | Gas sales revenues: | Public authority and other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	20,227	14,662	33,289	27,684
Operating Segments | Distribution | Transportation revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	30,973	28,504	58,740	55,144
Operating Segments | Distribution | Miscellaneous revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,325	6,986	5,721	13,772
Operating Segments | Pipeline and Storage
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	155,443	156,083	325,352	313,248
Alternative revenue program revenues	(1,275)	(9,846)	(11,471)	(18,835)
Other revenues	0	0	0	0
Total operating revenues	154,168	146,237	313,881	294,413
Operating Segments | Pipeline and Storage | Gas sales revenues:
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Operating Segments | Pipeline and Storage | Gas sales revenues: | Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Operating Segments | Pipeline and Storage | Gas sales revenues: | Commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Operating Segments | Pipeline and Storage | Gas sales revenues: | Industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Operating Segments | Pipeline and Storage | Gas sales revenues: | Public authority and other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Operating Segments | Pipeline and Storage | Transportation revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	151,565	154,748	316,326	306,758
Operating Segments | Pipeline and Storage | Miscellaneous revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,878	$ 1,335	$ 9,026	$ 6,490

Revenue and Accounts Receivab_4

Revenue and Accounts Receivable - Allowance for Credit Loss (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
Percent of customers excluded		78.00%
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 35,089	$ 29,949
Current period provisions	11,532	18,469
Write-offs charged against allowance	(2,381)	(4,669)
Recoveries of amounts previously written off	440	931
Ending balance	$ 44,680	$ 44,680

Debt - Schedule of Long-term De

Debt - Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 09, 2021	Oct. 01, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
Long-term debt	$ 7,360,000			$ 4,560,000
Finance lease obligations	8,612			8,631
Total long-term debt	7,368,612			4,568,631
Original issue discount on unsecured senior notes and debentures	3,030			583
Debt issuance cost	49,001			36,104
Current maturities	177			165
Long-term debt, noncurrent	$ 7,316,404			4,531,779
Unsecured 0.625% Senior Notes, due 2023
Debt Instrument [Line Items]
Interest rate	0.625%	0.625%
Long-term debt	$ 1,100,000			0
Unsecured 3.00% Senior Notes, due 2027
Debt Instrument [Line Items]
Interest rate	3.00%
Long-term debt	$ 500,000			500,000
Unsecured 2.625% Senior Notes, due 2029
Debt Instrument [Line Items]
Interest rate	2.625%
Long-term debt	$ 300,000			300,000
Unsecured 1.50% Senior Notes, due 2031
Debt Instrument [Line Items]
Interest rate	1.50%		1.50%
Long-term debt	$ 600,000			0
Unsecured 5.95% Senior Notes, due 2034
Debt Instrument [Line Items]
Interest rate	5.95%
Long-term debt	$ 200,000			200,000
Unsecured 5.50% Senior Notes, due 2041
Debt Instrument [Line Items]
Interest rate	5.50%
Long-term debt	$ 400,000			400,000
Unsecured 4.15% Senior Notes, due 2043
Debt Instrument [Line Items]
Interest rate	4.15%
Long-term debt	$ 500,000			500,000
Unsecured 4.125% Senior Notes, due 2044
Debt Instrument [Line Items]
Interest rate	4.125%
Long-term debt	$ 750,000			750,000
Unsecured 4.30% Senior Notes, due 2048
Debt Instrument [Line Items]
Interest rate	4.30%
Long-term debt	$ 600,000			600,000
Unsecured 4.125% Senior Notes, due 2049
Debt Instrument [Line Items]
Interest rate	4.125%
Long-term debt	$ 450,000			450,000
Unsecured 3.375% Senior Notes, due 2049
Debt Instrument [Line Items]
Interest rate	3.375%
Long-term debt	$ 500,000			500,000
Floating-rate term loan, due April 2022
Debt Instrument [Line Items]
Long-term debt	200,000			200,000
Floating-rate Senior Notes, due 2023
Debt Instrument [Line Items]
Long-term debt	$ 1,100,000			0
Medium-term note Series A, 1995-1, 6.67%, due 2025
Debt Instrument [Line Items]
Interest rate	6.67%
Long-term debt	$ 10,000			10,000
Unsecured 6.75% Debentures, due 2028
Debt Instrument [Line Items]
Interest rate	6.75%
Long-term debt	$ 150,000			$ 150,000

Debt - Narrative (Details)

Debt - Narrative (Details)	Mar. 31, 2021USD ($)credit_facility	Mar. 09, 2021USD ($)	Oct. 01, 2020USD ($)	Mar. 31, 2021USD ($)credit_facility	Mar. 30, 2021USD ($)	Mar. 31, 2020USD ($)	Sep. 30, 2020USD ($)
Line Of Credit Facility [Line Items]
Proceeds from issuance of long-term debt				$ 2,797,346,000		$ 799,450,000
Maximum debt-to-total-capitalization ratio				70.00%
Debt-to-total-capitalization ratio	0.49			0.49
Minimum
Line Of Credit Facility [Line Items]
Equity-to-total-capitalization ratio				50.00%
Outstanding indebtedness	$ 15,000,000			$ 15,000,000
Maximum
Line Of Credit Facility [Line Items]
Equity-to-total-capitalization ratio				60.00%
Outstanding indebtedness	100,000,000			$ 100,000,000
Revolving Credit Facility
Line Of Credit Facility [Line Items]
Maximum borrowing capacity	$ 2,500,000,000			$ 2,500,000,000
Number of credit facilities | credit_facility	4			4
Senior Notes Due 2023
Line Of Credit Facility [Line Items]
Debt instrument, face amount		$ 2,200,000,000
Proceeds net of issuance cost		$ 2,200,000,000
Redemption price (in percent)		100.00%
Unsecured 0.625% Senior Notes, due 2023
Line Of Credit Facility [Line Items]
Debt instrument, face amount		$ 1,100,000,000
Interest rate	0.625%	0.625%		0.625%
Effective Interest Rate		0.834%
Floating-rate Senior Notes, due 2023
Line Of Credit Facility [Line Items]
Debt instrument, face amount		$ 1,100,000,000
Unsecured 1.50% Senior Notes, due 2031
Line Of Credit Facility [Line Items]
Debt instrument, face amount			$ 600,000,000
Interest rate	1.50%		1.50%	1.50%
Effective Interest Rate			1.71%
Proceeds from issuance of long-term debt			$ 592,300,000
Five Year Unsecured Revolving Credit Agreement
Line Of Credit Facility [Line Items]
Outstanding commercial paper	$ 0			$ 0			$ 0
Five Year Unsecured Revolving Credit Agreement | Commercial Paper
Line Of Credit Facility [Line Items]
Maximum borrowing capacity	$ 1,500,000,000			1,500,000,000	$ 1,500,000,000
Debt agreement term	5 years				5 years
Accordion feature	$ 250,000,000			250,000,000
Maximum borrowing capacity post accordion feature	1,750,000,000			1,750,000,000
$600 Million Revolving Credit Facility | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Maximum borrowing capacity					$ 600,000,000
Debt agreement term					364 days
$900 Million Revolving Credit Facility | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Maximum borrowing capacity	$ 900,000,000			900,000,000
Debt agreement term	3 years
Accordion feature	$ 100,000,000			100,000,000
Maximum borrowing capacity post accordion feature	1,000,000,000			1,000,000,000
Outstanding borrowings	0			0
$50 Million Bank Loan Agreement | Line of Credit
Line Of Credit Facility [Line Items]
Maximum borrowing capacity	50,000,000			$ 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			0
$50 Million Revolving Credit Facility | Revolving Credit Facility
Line Of Credit Facility [Line Items]
Maximum borrowing capacity	50,000,000			$ 50,000,000
Debt agreement term				364 days
Remaining borrowing capacity	$ 44,400,000			$ 44,400,000
Base Rate | Five Year Unsecured Revolving Credit Agreement | Commercial Paper | Minimum
Line Of Credit Facility [Line Items]
Interest rate spread	0.00%
Base Rate | Five Year Unsecured Revolving Credit Agreement | Commercial Paper | Maximum
Line Of Credit Facility [Line Items]
Interest rate spread	0.25%
Base Rate | $900 Million Revolving Credit Facility | Revolving Credit Facility | Minimum
Line Of Credit Facility [Line Items]
Interest rate spread	0.00%
Base Rate | $900 Million Revolving Credit Facility | Revolving Credit Facility | Maximum
Line Of Credit Facility [Line Items]
Interest rate spread	0.25%
LIBOR | Floating-rate Senior Notes, due 2023
Line Of Credit Facility [Line Items]
Interest rate spread		0.38%
LIBOR | Five Year Unsecured Revolving Credit Agreement | Commercial Paper | Minimum
Line Of Credit Facility [Line Items]
Interest rate spread	0.75%
LIBOR | Five Year Unsecured Revolving Credit Agreement | Commercial Paper | Maximum
Line Of Credit Facility [Line Items]
Interest rate spread	1.25%
LIBOR | $900 Million Revolving Credit Facility | Revolving Credit Facility | Minimum
Line Of Credit Facility [Line Items]
Interest rate spread	0.75%
LIBOR | $900 Million Revolving Credit Facility | Revolving Credit Facility | Maximum
Line Of Credit Facility [Line Items]
Interest rate spread	1.25%

Shareholders' Equity - Componen

Shareholders' Equity - Components of Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2021	Mar. 31, 2020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock outstanding, beginning balance (in shares)		125,882,477			125,882,477
Shareholders' equity, beginning balance	$ 7,213,156	$ 6,791,203	$ 6,127,775	$ 5,750,223	$ 6,791,203	$ 5,750,223
Net income	296,754	217,678	239,646	178,673	514,432	418,319
Other comprehensive income (loss)	137,939	60,121	890	1,052	$ 198,060	1,942
Cash dividends	(80,325)	(79,023)	(70,520)	(69,557)
Public and other stock offerings	248,960	220,009	3,096	263,272
Stock-based compensation plans	$ 4,441	3,168	3,528	4,112
Common stock outstanding, ending balance (in shares)	130,667,109				130,667,109
Shareholders' equity, ending balance	$ 7,820,925	$ 7,213,156	$ 6,304,415	$ 6,127,775	$ 7,820,925	$ 6,304,415
Cash dividends per share (USD per share)	$ 0.625	$ 0.625	$ 0.575	$ 0.575	$ 1.25	$ 1.15
Common stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock outstanding, beginning balance (in shares)	128,152,961	125,882,477	122,262,403	119,338,925	125,882,477	119,338,925
Shareholders' equity, beginning balance	$ 641	$ 629	$ 611	$ 597	$ 629	$ 597
Public and other stock offerings (in shares)	2,498,026	2,126,118	38,662	2,758,929
Public and other stock offerings	$ 12	$ 11	$ 1	$ 13
Stock-based compensation plans (in shares)	16,122	144,366	7,660	164,549
Stock-based compensation plans	$ 0	$ 1	$ 0	$ 1
Common stock outstanding, ending balance (in shares)	130,667,109	128,152,961	122,308,725	122,262,403	130,667,109	122,308,725
Shareholders' equity, ending balance	$ 653	$ 641	$ 612	$ 611	$ 653	$ 612
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shareholders' equity, beginning balance	4,600,314	4,377,149	3,979,564	3,712,194	4,377,149	3,712,194
Public and other stock offerings	248,948	219,998	3,095	263,259
Stock-based compensation plans	4,441	3,167	3,528	4,111
Shareholders' equity, ending balance	4,853,703	4,600,314	3,986,187	3,979,564	4,853,703	3,986,187
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shareholders' equity, beginning balance	2,532	(57,589)	(113,531)	(114,583)	(57,589)	(114,583)
Other comprehensive income (loss)	137,939	60,121	890	1,052
Shareholders' equity, ending balance	140,471	2,532	(112,641)	(113,531)	140,471	(112,641)
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shareholders' equity, beginning balance	2,609,669	2,471,014	2,261,131	2,152,015	2,471,014	2,152,015
Net income	296,754	217,678	239,646	178,673
Cash dividends	(80,325)	(79,023)	(70,520)	(69,557)
Shareholders' equity, ending balance	$ 2,826,098	$ 2,609,669	$ 2,430,257	$ 2,261,131	$ 2,826,098	$ 2,430,257

Shareholders' Equity - Narrativ

Shareholders' Equity - Narrative (Details) - USD ($)	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Feb. 11, 2020
Class of Stock [Line Items]
Net proceeds from equity offering	$ 460,678,000	$ 258,047,000
Net proceeds available	$ 115,600,000
Forward Price (dollars per share)	$ 90.96
Shelf Registration Statement
Class of Stock [Line Items]
Debt and equity securities authorized for issuance			$ 4,000,000,000
Debt and equity securities authorized for issuance value remaining	$ 200,000,000
At-The-Market
Class of Stock [Line Items]
Forward sales equity agreement (in shares)	2,472,912
Stock issued during period, new issues (in shares)	4,537,669
Net proceeds from equity offering	$ 460,700,000
Equity available for issuance	313,000,000
Net proceeds available	$ 238,600,000

Shareholders' Equity - Schedule

Shareholders' Equity - Schedule of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	$ 7,213,156	$ 6,791,203	$ 6,127,775	$ 5,750,223	$ 6,791,203	$ 5,750,223
Other comprehensive income (loss) before reclassifications					195,777	(163)
Amounts reclassified from accumulated other comprehensive income					2,283	2,105
Net current-period other comprehensive income (loss)	137,939	60,121	890	1,052	198,060	1,942
Shareholders' equity, ending balance	7,820,925	7,213,156	6,304,415	6,127,775	7,820,925	6,304,415
Available- for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance		238		132	238	132
Other comprehensive income (loss) before reclassifications					(129)	(163)
Amounts reclassified from accumulated other comprehensive income					0	(1)
Net current-period other comprehensive income (loss)					(129)	(164)
Shareholders' equity, ending balance	109		(32)		109	(32)
Interest Rate Agreement Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance		(57,827)		(114,715)	(57,827)	(114,715)
Other comprehensive income (loss) before reclassifications					195,906	0
Amounts reclassified from accumulated other comprehensive income					2,283	2,106
Net current-period other comprehensive income (loss)					198,189	2,106
Shareholders' equity, ending balance	140,362		(112,609)		140,362	(112,609)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	2,532	(57,589)	(113,531)	(114,583)	(57,589)	(114,583)
Net current-period other comprehensive income (loss)	137,939	60,121	890	1,052
Shareholders' equity, ending balance	$ 140,471	$ 2,532	$ (112,641)	$ (113,531)	$ 140,471	$ (112,641)

Interim Pension and Other Pos_3

Interim Pension and Other Postretirement Benefit Plan Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Contribution to postretirement medical plans			$ 8,700
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4,613	$ 4,652	9,225	$ 9,305
Interest cost	5,028	5,843	10,056	11,686
Expected return on assets	(6,978)	(7,079)	(13,956)	(14,158)
Amortization of prior service cost (credit)	(58)	(58)	(116)	(116)
Amortization of actuarial (gain) loss	3,171	3,242	6,343	6,483
Net periodic pension cost	5,776	6,600	11,552	13,200
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	4,306	3,366	8,612	6,733
Interest cost	2,660	2,653	5,320	5,306
Expected return on assets	(2,614)	(2,625)	(5,228)	(5,249)
Amortization of prior service cost (credit)	43	43	86	87
Amortization of actuarial (gain) loss	0	(334)	0	(669)
Net periodic pension cost	4,395	$ 3,103	8,790	$ 6,208
Minimum | Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected future contributions	15,000		15,000
Maximum | Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected future contributions	$ 25,000		$ 25,000

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($)	Feb. 08, 2021	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Self-insurance retention expense		$ 1,000,000
Penalties incurred	$ 1,600,000

Financial Instruments - Narrati

Financial Instruments - Narrative (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)	Mar. 31, 2021USD ($)Bcf	Mar. 31, 2020USD ($)	Sep. 30, 2020USD ($)
Derivative [Line Items]
Contract netting	$ 0		$ 0		$ 0
Cash collateral	0		0		$ 0
Net gain (loss) on settled interest rate agreements	(1,500,000)	$ (1,400,000)	(2,900,000)	$ (2,700,000)
Net realized gain (loss) in AOCI	$ (112,200,000)		$ (112,200,000)
Gas Purchases | Not Designated as Hedging Instrument | Commodity contracts
Derivative [Line Items]
Hedging percent	39.00%		39.00%
Energy measure | Bcf			15.8
Gas Purchases | Not Designated as Hedging Instrument | Commodity contracts | Long
Derivative [Line Items]
Energy measure | Bcf			8.58
Minimum | Gas Purchases | Not Designated as Hedging Instrument | Commodity contracts
Derivative [Line Items]
Hedging percent	25.00%		25.00%
Maximum | Gas Purchases | Not Designated as Hedging Instrument | Commodity contracts
Derivative [Line Items]
Hedging percent	50.00%		50.00%

Financial Instruments - Forward

Financial Instruments - Forward Starting Derivatives (Details) - Designated as Hedging Instrument - Forward Interest Rate Swap	Mar. 31, 2021USD ($)
Derivative [Line Items]
Amount Hedged	$ 1,050,000,000
Unsecured Senior Notes In Fiscal 2022
Derivative [Line Items]
Amount Hedged	$ 450,000,000
Effective Interest Rate	1.33%
Unsecured Senior Notes In Fiscal 2023
Derivative [Line Items]
Amount Hedged	$ 300,000,000
Effective Interest Rate	1.36%
Unsecured Senior Notes In Fiscal 2025
Derivative [Line Items]
Amount Hedged	$ 300,000,000
Effective Interest Rate	1.35%

Financial Instruments - Schedul

Financial Instruments - Schedule of Derivative Instruments in Statement of Financial Position, Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Derivatives Fair Value [Line Items]
Net Financial Instruments, Assets	$ 327,158	$ 80,678
Net Financial Instruments, Liabilities	(62)	(2,015)
Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Gross Financial Instruments, Assets	325,584	73,055
Gross Financial Instruments, Liabilities	0	0
Designated as Hedging Instrument | Other Current Assets | Interest rate contracts
Derivatives Fair Value [Line Items]
Gross Financial Instruments, Assets	131,798
Designated as Hedging Instrument | Other Current Liabilities | Interest rate contracts
Derivatives Fair Value [Line Items]
Gross Financial Instruments, Liabilities	0
Designated as Hedging Instrument | Deferred Charges and Other Assets | Interest rate contracts
Derivatives Fair Value [Line Items]
Gross Financial Instruments, Assets	193,786	73,055
Designated as Hedging Instrument | Deferred Credits and Other Liabilities | Interest rate contracts
Derivatives Fair Value [Line Items]
Gross Financial Instruments, Liabilities	0	0
Not Designated as Hedging Instrument
Derivatives Fair Value [Line Items]
Gross Financial Instruments, Assets	1,574	7,623
Gross Financial Instruments, Liabilities	(62)	(2,015)
Not Designated as Hedging Instrument | Other Current Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Gross Financial Instruments, Assets	1,574	5,687
Not Designated as Hedging Instrument | Other Current Liabilities | Commodity contracts
Derivatives Fair Value [Line Items]
Gross Financial Instruments, Liabilities	$ (62)	(2,015)
Not Designated as Hedging Instrument | Deferred Charges and Other Assets | Commodity contracts
Derivatives Fair Value [Line Items]
Gross Financial Instruments, Assets		1,936
Not Designated as Hedging Instrument | Deferred Credits and Other Liabilities | Commodity contracts
Derivatives Fair Value [Line Items]
Gross Financial Instruments, Liabilities		$ 0

Financial Instruments - Sched_2

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, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Increase in fair value:
Interest rate agreements	$ 136,864	$ 0	$ 195,906	$ 0
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Interest rate agreements	1,141	1,053	2,283	2,106
Total other comprehensive income (loss) from hedging, net of tax	$ 138,005	$ 1,053	$ 198,189	$ 2,106

Financial Instruments - Sched_3

Financial Instruments - Schedule Of Expected Deferred Gains (Losses) Recognition (Details) $ in Thousands	6 Months Ended
	Mar. 31, 2021USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Next twelve months	$ (4,566)
Thereafter	(107,653)
Total	$ (112,219)

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($)	Mar. 31, 2021	Sep. 30, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Netting and Cash Collateral	$ 0	$ 0
Financial instruments net assets	327,158,000	80,678,000
Debt and equity securities	109,492,000	103,952,000
Total assets	436,650,000	184,630,000
Netting and Cash Collateral	0	0
Financial instruments net liability	62,000	2,015,000
Registered investment companies
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	34,501,000	37,831,000
Bond mutual funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	34,131,000	29,166,000
Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities	35,755,000	32,900,000
Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	5,105,000	4,055,000
Fair Value Inputs Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial instruments gross assets	0	0
Debt and equity securities	68,632,000	66,997,000
Total assets	68,632,000	66,997,000
Financial instruments gross liability	0	0
Fair Value Inputs Level 1 | Registered investment companies
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	34,501,000	37,831,000
Fair Value Inputs Level 1 | Bond mutual funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	34,131,000	29,166,000
Fair Value Inputs Level 1 | Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities	0	0
Fair Value Inputs Level 1 | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	0	0
Fair Value Inputs Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial instruments gross assets	327,158,000	80,678,000
Debt and equity securities	40,860,000	36,955,000
Total assets	368,018,000	117,633,000
Financial instruments gross liability	62,000	2,015,000
Fair Value Inputs Level 2 | Registered investment companies
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	0	0
Fair Value Inputs Level 2 | Bond mutual funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	0	0
Fair Value Inputs Level 2 | Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities	35,755,000	32,900,000
Fair Value Inputs Level 2 | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	5,105,000	4,055,000
Fair Value Inputs Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial instruments gross assets	0	0
Debt and equity securities	0	0
Total assets	0	0
Financial instruments gross liability	0	0
Fair Value Inputs Level 3 | Registered investment companies
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	0	0
Fair Value Inputs Level 3 | Bond mutual funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	0	0
Fair Value Inputs Level 3 | Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt securities	0	0
Fair Value Inputs Level 3 | Money market funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity Securities	$ 0	$ 0

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($)	Mar. 31, 2021	Sep. 30, 2020
Schedule of Available For Sale Securities [Abstract]
Allowance for credit losses	$ 0
Cost basis	$ 35,600,000	$ 32,600,000

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Debt Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Carrying Amount	$ 7,360,000	$ 4,560,000
Fair Value	$ 7,828,415	$ 5,597,183

Winter Storm Uri (Details)

Winter Storm Uri (Details) - USD ($)	1 Months Ended	6 Months Ended
	Feb. 28, 2021	Mar. 31, 2021	Mar. 09, 2021	Sep. 30, 2020
Unusual or Infrequent Item, or Both [Line Items]
Aggregate natural gas purchases	$ 2,300,000,000
Regulatory assets		$ 2,486,682,000		$ 414,641,000
Winter Storm Uri
Unusual or Infrequent Item, or Both [Line Items]
Increase (Decrease) Net Operating Loss Carryforwards		469,400,000
Increase (Decrease) in Deferred Income Taxes		469,400,000
Federal net operating loss carryforward		813,100,000
State net operating loss carryforward		57,500,000
State net operating loss carryforward, federal effects		15,300,000
State tax credit carryforwards		1,800,000
State tax credit carryforwards, federal effects		500,000
Winter Storm Uri incremental costs
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets		2,093,534,000		$ 0
Winter Storm Uri incremental costs | Winter Storm Uri
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets		2,100,000,000
Winter Storm Uri incremental costs | Kansas | Winter Storm Uri
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets		76,700,000
Winter Storm Uri incremental costs | Texas | Winter Storm Uri
Unusual or Infrequent Item, or Both [Line Items]
Regulatory assets		$ 2,016,800,000
Senior Notes Due 2023
Unusual or Infrequent Item, or Both [Line Items]
Debt instrument, face amount			$ 2,200,000,000