Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Thousands	Total	Series E Preferred Stock	Cumulative Effect, Period of Adoption, Adjustment	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)
Balance at beginning of period at Dec. 31, 2018	$ 3,267,570		$ (1,531)	$ 125,000		$ 56,518	$ 1,557,984		$ (5,634)	$ 1,610,574	$ (1,531)	$ (76,872)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	355,697									355,697
Other comprehensive income (loss), net of tax	42,194											42,194
Cash dividends declared on common stock	(56,910)									(56,910)
Dividends on preferred stock	(8,200)									(8,200)
Stock-based compensation	11,304						11,304
Common stock issued for:
Acquisitions	71,756					1,074	70,682
Exercise of stock options and warrants	4,843					146	5,541		(844)
Restricted stock awards	(453)					150	(150)		(453)
Employee stock purchase plan	2,819					44	2,775
Director compensation plan	2,161					19	2,142
Balance at end of period at Dec. 31, 2019	$ 3,691,250		$ (26,717)	125,000		57,951	1,650,278		(6,931)	1,899,630	$ (26,717)	(34,678)
Common stock issued for:
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Net income	$ 292,990									292,990
Other comprehensive income (loss), net of tax	50,060											50,060
Cash dividends declared on common stock	(64,513)									(64,513)
Dividends on preferred stock	(21,377)									(21,377)
Common stock repurchased under authorized program	(92,055)								(92,055)
Stock-based compensation	(4,938)						(4,938)
Issuance of Series E preferred stock		$ 277,613			$ 287,500			$ (9,887)
Acquisitions	0
Exercise of stock options and warrants	9,038					229	9,434		(625)
Restricted stock awards	(752)					201	(201)		(752)
Employee stock purchase plan	2,978					72	2,906
Director compensation plan	2,418					20	2,398
Balance at end of period 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	466,151									466,151
Other comprehensive income (loss), net of tax	(11,290)											(11,290)
Cash dividends declared on common stock	(70,663)									(70,663)
Dividends on preferred stock	(27,966)									(27,966)
Common stock repurchased under authorized program	(9,540)								(9,540)
Stock-based compensation	16,177						16,177
Common stock issued for:
Acquisitions	0
Exercise of stock options and warrants	14,035					327	13,708
Restricted stock awards						20	(20)
Employee stock purchase plan	3,325					48	3,277
Director compensation plan	2,464					24	2,440
Balance at end of period at Dec. 31, 2021	$ 4,498,688			$ 412,500		$ 58,892	$ 1,685,572		$ (109,903)	$ 2,447,535		$ 4,092