CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Preferred stock	Common stock	Surplus	Treasury stock	Retained earnings	Accumulated other comprehensive income (loss)
Beginning balance at Dec. 31, 2020	$ 4,115,995	$ 412,500	$ 58,473	$ 1,649,990	$ (100,363)	$ 2,080,013	$ 15,382
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	153,148					153,148
Other comprehensive loss, net of tax	(5,278)						(5,278)
Cash dividends declared on common stock	(17,635)					(17,635)
Dividends on preferred stock	(6,991)					(6,991)
Stock-based compensation	2,862			2,862
Common stock issued for:
Exercise of stock options and warrants	8,961		209	8,752
Restricted stock awards	0		7	(7)
Employee stock purchase plan	815		14	801
Director compensation plan	634		24	610
Ending balance at Mar. 31, 2021	4,252,511	412,500	58,727	1,663,008	(100,363)	2,208,535	10,104
Beginning balance 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	127,391					127,391
Other comprehensive loss, net of tax	(120,091)						(120,091)
Cash dividends declared on common stock	(19,461)					(19,461)
Dividends on preferred stock	(6,991)					(6,991)
Stock-based compensation	7,891			7,891
Common stock issued for:
Exercise of stock options and warrants	3,358		79	3,279
Restricted stock awards	0		52	(52)
Employee stock purchase plan	842		10	832
Director compensation plan	629		58	571
Ending balance at Mar. 31, 2022	$ 4,492,256	$ 412,500	$ 59,091	$ 1,698,093	$ (109,903)	$ 2,548,474	$ (115,999)