CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 774,398	$ 665,563	$ 601,443
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	535,655	477,977	429,828
Deferred income taxes	53,651	155,355	155,322
One-time income tax benefit	0	0	(20,962)
Stock-based compensation	10,743	11,255	9,583
Amortization of debt issuance costs	9,141	14,030	11,543
Equity component of AFUDC	(45,505)	(32,749)	(23,493)
Other	3,265	3,731	8,411
Changes in assets and liabilities:
(Increase) decrease in accounts receivable	(34,325)	(113,665)	7,167
(Increase) decrease in gas stored underground	(179,825)	(66,166)	18,188
Increase in Winter Storm Uri current regulatory asset (see Note 9)	0	(2,003,659)	0
Increase in other current assets	(65,979)	(84,705)	(35,878)
Increase in Winter Storm Uri long-term regulatory asset (see Note 9)	0	(76,652)	0
(Increase) decrease in deferred charges and other assets	13,287	136,809	(31,935)
Increase in accounts payable and accrued liabilities	40,394	104,242	7,359
Decrease in other current liabilities	(152,274)	(166,268)	(129,543)
Increase (decrease) in deferred credits and other liabilities	14,958	(109,349)	30,966
Net cash provided by (used in) operating activities	977,584	(1,084,251)	1,037,999
CASH FLOWS USED IN INVESTING ACTIVITIES
Capital expenditures	(2,444,420)	(1,969,540)	(1,935,676)
Purchases of debt and equity securities	(28,285)	(49,879)	(50,517)
Proceeds from sale of debt and equity securities	4,872	14,957	32,339
Maturities of debt securities	27,586	28,850	18,669
Other, net	10,289	11,957	9,667
Net cash used in investing activities	(2,429,958)	(1,963,655)	(1,925,518)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in short-term debt	184,967	0	(464,915)
Proceeds from issuance of long-term debt, net of premium/discount	798,802	2,797,346	999,450
Net proceeds from equity offering	776,805	606,667	624,302
Issuance of common stock through stock purchase and employee retirement plans	15,403	15,841	19,548
Settlement of interest rate swaps	197,073	62,159	(4,426)
Repayment of long-term debt	(200,000)	0	0
Cash dividends paid	(375,914)	(323,904)	(282,444)
Debt issuance costs	(8,196)	(14,288)	(7,738)
Other	(1,735)	0	0
Net cash provided by financing activities	1,387,205	3,143,821	883,777
Net increase (decrease) in cash and cash equivalents	(65,169)	95,915	(3,742)
Cash and cash equivalents at beginning of year	116,723	20,808	24,550
Cash and cash equivalents at end of year	$ 51,554	$ 116,723	$ 20,808