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	258,257					258,257
Other comprehensive income (loss), net of tax	(5,249)						(5,249)
Cash dividends declared on common stock	(35,319)					(35,319)
Dividends on preferred stock	(13,982)					(13,982)
Stock-based compensation	6,194			6,194
Common stock issued for:
Exercise of stock options and warrants	10,241		238	10,003
Restricted stock awards			10	(10)
Employee stock purchase plan	1,620		25	1,595
Director compensation plan	1,254		24	1,230
Ending balance at Jun. 30, 2021	4,339,011	412,500	58,770	1,669,002	(100,363)	2,288,969	10,133
Beginning balance at Mar. 31, 2021	4,252,511	412,500	58,727	1,663,008	(100,363)	2,208,535	10,104
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	105,109					105,109
Other comprehensive income (loss), net of tax	29						29
Cash dividends declared on common stock	(17,684)					(17,684)
Dividends on preferred stock	(6,991)					(6,991)
Stock-based compensation	3,332			3,332
Common stock issued for:
Exercise of stock options and warrants	1,280		29	1,251
Restricted stock awards			3	(3)
Employee stock purchase plan	805		11	794
Director compensation plan	620			620
Ending balance at Jun. 30, 2021	4,339,011	412,500	58,770	1,669,002	(100,363)	2,288,969	10,133
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	221,904					221,904
Other comprehensive income (loss), net of tax	(247,129)						(247,129)
Cash dividends declared on common stock	(38,932)					(38,932)
Dividends on preferred stock	(13,982)					(13,982)
Stock-based compensation	14,889			14,889
Common stock issued for:
New issuance, net of cost	285,721		1,612	174,206	109,903
Exercise of stock options and warrants	3,540		84	3,456
Restricted stock awards			56	(56)
Employee stock purchase plan	1,635		19	1,616
Director compensation plan	1,289		59	1,230
Ending balance at Jun. 30, 2022	4,727,623	412,500	60,722	1,880,913	0	2,616,525	(243,037)
Beginning balance at Mar. 31, 2022	4,492,256	412,500	59,091	1,698,093	(109,903)	2,548,474	(115,999)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	94,513					94,513
Other comprehensive income (loss), net of tax	(127,038)						(127,038)
Cash dividends declared on common stock	(19,471)					(19,471)
Dividends on preferred stock	(6,991)					(6,991)
Stock-based compensation	6,998			6,998
Common stock issued for:
New issuance, net of cost	285,721		1,612	174,206	109,903
Exercise of stock options and warrants	182		5	177
Restricted stock awards			4	(4)
Employee stock purchase plan	793		9	784
Director compensation plan	660		1	659
Ending balance at Jun. 30, 2022	$ 4,727,623	$ 412,500	$ 60,722	$ 1,880,913	$ 0	$ 2,616,525	$ (243,037)