CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Series E Preferred Stock	Preferred stock	Preferred stock Series E Preferred Stock	Common stock	Surplus	Surplus Series E Preferred Stock	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	221,904									221,904
Other comprehensive loss, net of tax	(247,129)											(247,129)
Cash dividends declared on common stock	(38,932)									(38,932)
Dividends on Series D and E preferred stock	(13,982)									(13,982)
Common stock repurchases under authorized program	0								0
Stock-based compensation	14,889						14,889
Issuance of Series E preferred stock (in shares)					0
Issuance of Series E preferred stock			$ 0					$ 0
Common stock issued for:
Acquisitions	285,721					1,612	174,206		109,903
New issuance, net of cost			0					0
Exercise of stock options and warrants	3,540					84	3,456
Restricted stock awards	0					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 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 [Member]
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 loss, net of tax	(127,038)											(127,038)
Cash dividends declared on common stock	(19,471)									(19,471)
Dividends on Series D and E preferred stock	(6,991)									(6,991)
Stock-based compensation	6,998						6,998
Issuance of Series E preferred stock (in shares)					0
Issuance of Series E preferred stock	285,721		0			1,612	174,206	0	109,903
Common stock issued for:
New issuance, net of cost	285,721		0			1,612	174,206	0	109,903
Exercise of stock options and warrants	182					5	177
Restricted stock awards	0					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)
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	334,948									334,948
Other comprehensive loss, net of tax	(46,454)											(46,454)
Cash dividends declared on common stock	(48,803)									(48,803)
Dividends on Series D and E preferred stock	(13,982)									(13,982)
Common stock repurchases under authorized program	0								0
Stock-based compensation	16,403						16,403
Issuance of Series E preferred stock (in shares)					0
Issuance of Series E preferred stock	0		0			0	0	0	0
Common stock issued for:
New issuance, net of cost	0		$ 0			0	0	$ 0	0
Exercise of stock options and warrants	2,216					54	2,162
Restricted stock awards	(1,662)					283	(283)		(1,662)
Employee stock purchase plan	1,601					22	1,579
Director compensation plan	1,351					63	1,288
Ending balance at Jun. 30, 2023	$ 5,041,912			412,500		61,219	1,923,623		(1,966)	3,120,626		(474,090)
Common stock issued for:
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2016-13 [Member]
Beginning balance at Mar. 31, 2023	$ 5,015,506			412,500		61,198	1,913,947		(1,966)	2,997,263		(367,436)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	154,750									154,750
Other comprehensive loss, net of tax	(106,654)											(106,654)
Cash dividends declared on common stock	(24,396)									(24,396)
Dividends on Series D and E preferred stock	(6,991)									(6,991)
Stock-based compensation	8,108						8,108
Common stock issued for:
Exercise of stock options and warrants	0					0	0
Restricted stock awards	0					8	(8)		0
Employee stock purchase plan	907					13	894
Director compensation plan	682					0	682
Ending balance at Jun. 30, 2023	$ 5,041,912			$ 412,500		$ 61,219	$ 1,923,623		$ (1,966)	$ 3,120,626		$ (474,090)