CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred stock	Common stock	Surplus	Treasury stock	Retained earnings	Retained earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated other comprehensive income (loss)
Balance at beginning of period at Dec. 31, 2021	$ 4,498,688		$ 412,500	$ 58,892	$ 1,685,572	$ (109,903)	$ 2,447,535		$ 4,092
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	509,682						509,682
Other comprehensive (loss) income , net of tax	(431,728)								(431,728)
Cash dividends declared on common stock	(80,246)						(80,246)
Dividends on Series D and E preferred stock	(27,964)						(27,964)
Stock-based compensation	31,748				31,748
Common stock issued for:
Acquisition of Macatawa Bank Corporation	0
New issuance, net of costs	285,729			1,612	174,214	109,903
Exercise of stock options and warrants	4,886			123	5,067	(304)
Restricted stock awards	0			69	(69)
Employee stock purchase plan	3,386			42	3,344
Director compensation plan	2,657			59	2,598
Balance at end of period at Dec. 31, 2022	$ 4,796,838	$ (544)	412,500	60,797	1,902,474	(304)	2,849,007	$ (544)	(427,636)
Common stock issued for:
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2022-02
Net income	$ 622,626						622,626
Other comprehensive (loss) income , net of tax	66,405								66,405
Cash dividends declared on common stock	(97,726)						(97,726)
Dividends on Series D and E preferred stock	(27,964)						(27,964)
Stock-based compensation	33,495				33,495
Acquisition of Macatawa Bank Corporation	0
Exercise of stock options and warrants	2,242			56	2,186
Restricted stock awards	(1,913)			307	(307)	(1,913)
Employee stock purchase plan	3,329			46	3,283
Director compensation plan	2,738			63	2,675
Balance at end of period at Dec. 31, 2023	5,399,526		412,500	61,269	1,943,806	(2,217)	3,345,399		(361,231)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	695,045						695,045
Other comprehensive (loss) income , net of tax	(147,104)								(147,104)
Cash dividends declared on common stock	(115,316)						(115,316)
Dividends on Series D and E preferred stock	(27,964)						(27,964)
Stock-based compensation	38,108				38,108
Common stock issued for:
Acquisition of Macatawa Bank Corporation	499,239			4,702	494,537
Exercise of stock options and warrants	86			2	84
Restricted stock awards	(3,931)			537	(532)	(3,936)
Employee stock purchase plan	3,347			35	3,312
Director compensation plan	3,261			15	3,246
Balance at end of period at Dec. 31, 2024	$ 6,344,297		$ 412,500	$ 66,560	$ 2,482,561	$ (6,153)	$ 3,897,164		$ (508,335)