CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance, beginning of period 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	50,281				50,281
Other comprehensive income (loss)	(7,909)					(7,909)
Dividends on common stock	(14,899)				(14,899)
Dividends on preferred stock	(3,656)				(3,656)
Proceeds from stock-based awards	828		30	798
Stock-based compensation expense	1,390		173	1,217
Treasury stock acquired	(2,973)						(2,973)
Balance, end of period at Dec. 31, 2021	2,149,126	300,000	136,196	1,680,637	1,560,337	61,876	(1,589,920)
Balance, beginning of period 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	79,509				79,509
Other comprehensive income (loss)	(10,755)					(10,755)
Dividends on common stock	(15,585)				(15,585)
Dividends on preferred stock	(3,656)				(3,656)
Proceeds from stock-based awards	765		25	740
Stock-based compensation expense	1,571		77	1,494
Treasury stock acquired	(1,728)						(1,728)
Balance, end of period at Dec. 31, 2022	$ 2,324,381	$ 300,000	$ 136,373	$ 1,689,209	$ 1,749,008	$ 41,726	$ (1,591,935)