CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 1,198,754	$ 1,042,895	$ 885,862
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	734,745	669,972	604,327
Deferred income taxes	268,606	172,707	108,215
Stock-based compensation	12,731	10,709	10,178
Amortization of debt issuance costs	(14,962)	(6,882)	3,639
Equity component of AFUDC	(75,425)	(58,234)	(64,019)
Other	11,003	1,546	(591)
Changes in assets and liabilities:
(Increase) decrease in accounts receivable	(1,417)	(40,909)	46,859
(Increase) decrease in gas stored underground	(2,248)	76,322	112,111
Decrease in Winter Storm Uri current regulatory asset (see Note 10)	0	0	2,021,889
(Increase) decrease in other current assets	19,517	17,138	(36,041)
Increase in deferred charges and other assets	(211,286)	(195,369)	(172,586)
Increase (decrease) in accounts payable and accrued liabilities	31,558	(4,563)	(132,575)
Increase (decrease) in other current liabilities	31,406	(10,287)	30,687
Increase in deferred credits and other liabilities	46,474	58,701	41,788
Net cash provided by operating activities	2,049,456	1,733,746	3,459,743
CASH FLOWS USED IN INVESTING ACTIVITIES
Capital expenditures	(3,561,399)	(2,937,124)	(2,805,973)
Purchases of debt and equity securities	(34,323)	(19,734)	(46,789)
Proceeds from sale of debt and equity securities	7,267	5,977	25,134
Maturities of debt securities	22,801	12,050	13,340
Other, net	4,372	16,062	19,008
Net cash used in investing activities	(3,561,282)	(2,922,769)	(2,795,280)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in short-term debt	0	(241,933)	56,966
Proceeds from issuance of long-term debt, net of premium/discount	1,143,447	1,240,204	797,258
Proceeds from issuance of securitized long-term debt by AEK	0	0	95,000
Net proceeds from equity offering	698,462	749,987	806,949
Issuance of common stock through stock purchase and employee retirement plans	15,277	15,084	15,395
Settlement of interest rate swaps	122,874	231,138	171,145
Proceeds from term loan	0	0	2,020,000
Repayment of term loan	0	0	(2,020,000)
Repayment of long-term debt	0	0	(2,200,000)
Repayment of securitized long-term debt by AEK	(8,075)	(9,922)	0
Cash dividends paid	(553,761)	(492,950)	(430,345)
Debt issuance costs	(10,384)	(11,844)	(7,864)
Securitized debt issuance costs	0	0	(1,273)
Other	(1,067)	(1,133)	0
Net cash provided by (used in) financing activities	1,406,773	1,478,631	(696,769)
Net increase (decrease) in cash and cash equivalents and restricted cash and cash equivalents	(105,053)	289,608	(32,306)
Cash and cash equivalents and restricted cash and cash equivalents at beginning of year	308,856	19,248	51,554
Cash and cash equivalents and restricted cash and cash equivalents at end of year	$ 203,803	$ 308,856	$ 19,248