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, 2023			97,584,000
Balance as of beginning of period at Sep. 30, 2023		$ 1,990,735	$ 243,458	$ 558,654	$ (9,959)	$ 20,748	$ 1,177,834
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		89,411					89,411
Other comprehensive income		395			395
Common stock issued:
Incentive compensation plan (in shares)			116,000
Incentive compensation plan		3,741	$ 290	3,451
Dividend reinvestment plan (in shares)	[1]		94,000
Dividend reinvestment plan	[1]	3,788	$ 236	3,552
Waiver discount (in shares)			410,000
Waiver discount		17,919	$ 1,025	16,894
Cash dividend declared		(41,176)					(41,176)
Treasury stock and other (in shares)			(2,000)
Treasury stock and other		1,388				1,388
Balance as of end of period (in shares) at Dec. 31, 2023			98,202,000
Balance as of end of period at Dec. 31, 2023		$ 2,066,201	$ 245,009	582,551	(9,564)	22,136	1,226,069
Balance as of beginning of period (in shares) at Sep. 30, 2024		99,461,448	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		$ (6,032)				(6,032)
Balance as of end of period (in shares) at Dec. 31, 2024		100,191,159	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

[1] Certain shares sold through the DRP issued from treasury stock are at average cost, which may differ from the actual market price paid.