CONDENSED CONSOLIDATED STATEMENTS OF COMMON STOCK EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Premium on Common Stock	Accumulated Other Comprehensive (Loss) Income	Treasury Stock and Other	Retained Earnings
Balance as of beginning of period (in shares) at Sep. 30, 2024		99,461,000
Balance as of beginning of period at Sep. 30, 2024	$ 2,200,443	$ 248,159	$ 633,811	$ (6,521)	$ 26,220	$ 1,298,774
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	131,319					131,319
Other comprehensive income	68			68
Common stock issued:
Incentive compensation plan (in shares)		232,000
Incentive compensation plan	8,242	$ 581	7,661
Dividend reinvestment plan (in shares)		80,000
Dividend reinvestment plan	3,744	$ 199	3,545
Waiver discount (in shares)		418,000
Waiver discount	19,910	$ 1,045	18,865
Cash dividend declared	(45,010)					(45,010)
Treasury stock and other (in shares)		0
Treasury stock and other	(6,032)				(6,032)
Balance as of end of period (in shares) at Dec. 31, 2024		100,191,000
Balance as of end of period at Dec. 31, 2024	$ 2,312,684	$ 249,984	663,882	(6,453)	20,188	1,385,083
Balance as of beginning of period (in shares) at Sep. 30, 2025	100,478,590	100,479,000
Balance as of beginning of period at Sep. 30, 2025	$ 2,391,666	$ 250,705	676,635	(11,463)	24,422	1,451,367
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	122,490					122,490
Other comprehensive income	258			258
Common stock issued:
Incentive compensation plan (in shares)		194,000
Incentive compensation plan	8,890	$ 485	8,405
Dividend reinvestment plan (in shares)		79,000
Dividend reinvestment plan	3,733	$ 198	3,535
Cash dividend declared	(47,855)					(47,855)
Treasury stock and other (in shares)		(2,000)
Treasury stock and other	$ (6,847)				(6,847)
Balance as of end of period (in shares) at Dec. 31, 2025	100,750,110	100,750,000
Balance as of end of period at Dec. 31, 2025	$ 2,472,335	$ 251,388	$ 688,575	$ (11,205)	$ 17,575	$ 1,526,002