Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance at Sep. 30, 2020	$ 2,014,133	$ 0	$ 135,727	$ 1,678,843	$ 1,420,906	$ 16,953	$ (1,238,296)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	183,615				183,615
Other comprehensive income (loss)	52,832					52,832
Issuance of preferred stock, net	293,325	300,000		(6,675)
Dividends on common stock	(65,876)				(65,876)
Dividends on preferred stock	(10,034)				(10,034)
Proceeds from stock issuances	339		20	319
Stock-based compensation expense	6,381		246	6,135
Treasury stock purchased	(348,651)						(348,651)
Ending balance at Sep. 30, 2021	2,126,064	300,000	135,993	1,678,622	1,528,611	69,785	(1,586,947)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	236,330				236,330
Other comprehensive income (loss)	(17,304)					(17,304)
Dividends on common stock	(61,576)				(61,576)
Dividends on preferred stock	(14,625)				(14,625)
Proceeds from stock issuances	1,823		65	1,758
Stock-based compensation expense	6,808		213	6,595
Treasury stock purchased	(3,260)						(3,260)
Ending balance at Sep. 30, 2022	2,274,260	300,000	136,271	1,686,975	1,688,740	52,481	(1,590,207)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	257,426				257,426
Other comprehensive income (loss)	(5,560)					(5,560)
Dividends on common stock	(63,792)				(63,792)
Dividends on preferred stock	(14,625)				(14,625)
Proceeds from stock issuances	1,266		42	1,224
Stock-based compensation expense	7,914		154	(565)			8,325
Treasury stock purchased	(30,463)						(30,463)
Ending balance at Sep. 30, 2023	$ 2,426,426	$ 300,000	$ 136,467	$ 1,687,634	$ 1,867,749	$ 46,921	$ (1,612,345)