CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 885,862	$ 774,398	$ 665,563
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	604,327	535,655	477,977
Deferred income taxes	108,215	53,651	155,355
Stock-based compensation	10,178	10,743	11,255
Amortization of debt issuance costs	3,639	9,141	14,030
Equity component of AFUDC	(64,019)	(45,505)	(32,749)
Other	(591)	3,265	3,731
Changes in assets and liabilities:
(Increase) decrease in accounts receivable	46,859	(34,325)	(113,665)
(Increase) decrease in gas stored underground	112,111	(179,825)	(66,166)
(Increase) decrease in Winter Storm Uri current regulatory asset (see Note 3)	2,021,889	0	(2,003,659)
Increase in other current assets	(36,041)	(65,979)	(84,705)
Increase in Winter Storm Uri long-term regulatory asset (see Note 3)	0	0	(76,652)
(Increase) decrease in deferred charges and other assets	(172,586)	13,287	136,809
Increase (decrease) in accounts payable and accrued liabilities	(132,575)	40,394	104,242
Increase (decrease) in other current liabilities	30,687	(152,274)	(166,268)
Increase (decrease) in deferred credits and other liabilities	41,788	14,958	(109,349)
Net cash provided by (used in) operating activities	3,459,743	977,584	(1,084,251)
CASH FLOWS USED IN INVESTING ACTIVITIES
Capital expenditures	(2,805,973)	(2,444,420)	(1,969,540)
Purchases of debt and equity securities	(46,789)	(28,285)	(49,879)
Proceeds from sale of debt and equity securities	25,134	4,872	14,957
Maturities of debt securities	13,340	27,586	28,850
Other, net	19,008	10,289	11,957
Net cash used in investing activities	(2,795,280)	(2,429,958)	(1,963,655)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase in short-term debt	56,966	184,967	0
Proceeds from issuance of long-term debt, net of premium/discount	797,258	798,802	2,797,346
Proceeds from issuance of securitized long-term debt by AEK	95,000	0	0
Net proceeds from equity offering	806,949	776,805	606,667
Issuance of common stock through stock purchase and employee retirement plans	15,395	15,403	15,841
Settlement of interest rate swaps	171,145	197,073	62,159
Proceeds from term loan	2,020,000	0	0
Repayment of term loan	(2,020,000)	0	0
Repayment of long-term debt	(2,200,000)	(200,000)	0
Cash dividends paid	(430,345)	(375,914)	(323,904)
Debt issuance costs	(7,864)	(8,196)	(14,288)
Securitized debt issuance costs	(1,273)	0	0
Other	0	(1,735)	0
Net cash provided by (used in) financing activities	(696,769)	1,387,205	3,143,821
Net increase (decrease) in cash and cash equivalents and restricted cash and cash equivalents	(32,306)	(65,169)	95,915
Cash and cash equivalents and restricted cash and cash equivalents at beginning of year	51,554	116,723	20,808
Cash and cash equivalents and restricted cash and cash equivalents at end of year	$ 19,248	$ 51,554	$ 116,723