CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) - 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, 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	207,218				207,218
Other comprehensive income (loss)	(5,130)					(5,130)
Dividends on common stock	(47,826)				(47,826)
Dividends on preferred stock	(10,968)				(10,968)
Proceeds from stock issuances	1,039		34	1,005
Stock-based compensation expense	5,923		153	(2,393)			8,163
Treasury stock purchased	(30,450)						(30,450)
Balance, end of period at Jun. 30, 2023	2,394,066	300,000	136,458	1,685,587	1,837,164	47,351	(1,612,494)
Balance, beginning of period at Mar. 31, 2023	2,375,117	300,000	136,413	1,683,720	1,795,042	43,822	(1,583,880)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	61,775				61,775
Other comprehensive income (loss)	3,529					3,529
Dividends on common stock	(15,998)				(15,998)
Dividends on preferred stock	(3,655)				(3,655)
Proceeds from stock issuances	16		1	15
Stock-based compensation expense	1,896		44	1,852
Treasury stock purchased	(28,614)						(28,614)
Balance, end of period at Jun. 30, 2023	2,394,066	300,000	136,458	1,685,587	1,837,164	47,351	(1,612,494)
Balance, beginning of period at Sep. 30, 2023	2,426,426	300,000	136,467	1,687,634	1,867,749	46,921	(1,612,345)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	138,901				138,901
Other comprehensive income (loss)	7,995					7,995
Dividends on common stock	(53,404)				(53,404)
Dividends on preferred stock	(10,969)				(10,969)
Stock issued in merger	465,504		17,089	448,415
Proceeds from stock issuances	3,268		122	3,146
Stock-based compensation expense	7,437		262	6,954			221
Treasury stock purchased	(26,819)						(26,819)
Balance, end of period at Jun. 30, 2024	2,958,339	300,000	153,940	2,146,149	1,942,277	54,916	(1,638,943)
Balance, beginning of period at Mar. 31, 2024	2,921,906	300,000	153,835	2,143,343	1,902,305	51,935	(1,629,512)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	64,560				64,560
Other comprehensive income (loss)	2,981					2,981
Dividends on common stock	(20,932)				(20,932)
Dividends on preferred stock	(3,656)				(3,656)
Proceeds from stock issuances	738		27	711
Stock-based compensation expense	2,257		78	2,095			84
Treasury stock purchased	(9,515)						(9,515)
Balance, end of period at Jun. 30, 2024	$ 2,958,339	$ 300,000	$ 153,940	$ 2,146,149	$ 1,942,277	$ 54,916	$ (1,638,943)