CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) - 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)
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	364,865						364,865
Other comprehensive loss, net of tax	(462,820)								(462,820)
Cash dividends declared on common stock	(59,583)						(59,583)
Dividends on Series D and E preferred stock	(20,973)						(20,973)
Stock-based compensation	23,852				23,852
Common stock issued for:
New Issuance, net of cost	285,721			1,612	174,206	109,903
Exercise of stock options	3,738			88	3,650
Restricted stock awards	0			61	(61)
Employee stock purchase plan	2,529			31	2,498
Director compensation plan	1,963			59	1,904
Ending balance at Sep. 30, 2022	4,637,980		412,500	60,743	1,891,621	0	2,731,844		(458,728)
Beginning balance at Dec. 31, 2021	4,498,688		412,500	58,892	1,685,572	(109,903)	2,447,535		4,092
Ending balance 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	Accounting Standards Update 2022-02
Beginning balance at Jun. 30, 2022	$ 4,727,623		412,500	60,722	1,880,913	0	2,616,525		(243,037)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	142,961						142,961
Other comprehensive loss, net of tax	(215,691)								(215,691)
Cash dividends declared on common stock	(20,651)						(20,651)
Dividends on Series D and E preferred stock	(6,991)						(6,991)
Stock-based compensation	8,963				8,963
Common stock issued for:
Exercise of stock options	198			4	194
Restricted stock awards	0			5	(5)
Employee stock purchase plan	894			12	882
Director compensation plan	674				674
Ending balance at Sep. 30, 2022	4,637,980		412,500	60,743	1,891,621	0	2,731,844		(458,728)
Beginning balance at Dec. 31, 2022	4,796,838	$ (544)	412,500	60,797	1,902,474	(304)	2,849,007	$ (544)	(427,636)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	499,146						499,146
Other comprehensive loss, net of tax	(215,087)								(215,087)
Cash dividends declared on common stock	(73,304)						(73,304)
Dividends on Series D and E preferred stock	(20,973)						(20,973)
Stock-based compensation	24,532				24,532
Common stock issued for:
Exercise of stock options	2,216			54	2,162
Restricted stock awards	(1,662)			296	(296)	(1,662)
Employee stock purchase plan	2,418			34	2,384
Director compensation plan	2,033			63	1,970
Ending balance at Sep. 30, 2023	5,015,613		412,500	61,244	1,933,226	(1,966)	3,253,332		(642,723)
Beginning balance at Jun. 30, 2023	5,041,912		412,500	61,219	1,923,623	(1,966)	3,120,626		(474,090)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	164,198						164,198
Other comprehensive loss, net of tax	(168,633)								(168,633)
Cash dividends declared on common stock	(24,501)						(24,501)
Dividends on Series D and E preferred stock	(6,991)						(6,991)
Stock-based compensation	8,130				8,130
Common stock issued for:
Restricted stock awards	0			13	(13)
Employee stock purchase plan	816			12	804
Director compensation plan	682				682
Ending balance at Sep. 30, 2023	$ 5,015,613		$ 412,500	$ 61,244	$ 1,933,226	$ (1,966)	$ 3,253,332		$ (642,723)