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	99,640				99,640
Other comprehensive income (loss)	1,693					1,693
Dividends on common stock	(30,456)				(30,456)
Dividends on preferred stock	(7,312)				(7,312)
Proceeds from stock-based awards	1,361		49	1,312
Stock-based compensation expense	3,846		202	3,644
Treasury stock acquired	(3,135)						(3,135)
Balance, end of period at Mar. 31, 2022	2,191,701	300,000	136,244	1,683,578	1,590,483	71,478	(1,590,082)
Balance, beginning of period at Dec. 31, 2021	2,149,126	300,000	136,196	1,680,637	1,560,337	61,876	(1,589,920)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	49,359				49,359
Other comprehensive income (loss)	9,602					9,602
Dividends on common stock	(15,557)				(15,557)
Dividends on preferred stock	(3,656)				(3,656)
Proceeds from stock-based awards	533		19	514
Stock-based compensation expense	2,456		29	2,427
Treasury stock acquired	(162)						(162)
Balance, end of period at Mar. 31, 2022	2,191,701	300,000	136,244	1,683,578	1,590,483	71,478	(1,590,082)
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	145,443				145,443
Other comprehensive income (loss)	(8,659)					(8,659)
Dividends on common stock	(31,828)				(31,828)
Dividends on preferred stock	(7,313)				(7,313)
Proceeds from stock-based awards	1,023		33	990
Stock-based compensation expense	4,027		109	(4,245)			8,163
Treasury stock acquired	(1,836)						(1,836)
Balance, end of period at Mar. 31, 2023	2,375,117	300,000	136,413	1,683,720	1,795,042	43,822	(1,583,880)
Balance, beginning of period at Dec. 31, 2022	2,324,381	300,000	136,373	1,689,209	1,749,008	41,726	(1,591,935)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	65,934				65,934
Other comprehensive income (loss)	2,096					2,096
Dividends on common stock	(16,243)				(16,243)
Dividends on preferred stock	(3,657)				(3,657)
Proceeds from stock-based awards	258		9	249
Stock-based compensation expense	2,456		31	(5,738)			8,163
Treasury stock acquired	(108)						(108)
Balance, end of period at Mar. 31, 2023	$ 2,375,117	$ 300,000	$ 136,413	$ 1,683,720	$ 1,795,042	$ 43,822	$ (1,583,880)