Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Preferred Stock [Member]	Common Stock	Capital Surplus [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Deferred Benefits for Directors [Member]
Beginning Balance at Dec. 31, 2019	$ 2,593,921	$ (26,591)		$ 141,827	$ 1,636,966	$ 824,694	$ (26,591)	$ (9,463)	$ 1,201	$ (1,304)
Beginning Balance, shares at Dec. 31, 2019				67,824,428
Net income	23,396					23,396
Other comprehensive income (loss)	39,940								39,940
Comprehensive income	63,336
Common dividends declared	$ (21,435)					(21,435)
Accounting Standards Update [Extensible List]	ASU 2016-13 [Member]
Treasury shares acquired	$ (24,972)							(24,972)
Treasury shares acquired, shares				(786,012)
Stock options exercised	445				(276)			721
Stock options exercised, shares				19,739
Stock compensation expense	1,370				1,370
Deferred benefits for directors- net	(14)				62					(76)
Ending Balance at Mar. 31, 2020	2,586,060			$ 141,827	1,638,122	800,064		(33,714)	41,141	(1,380)
Ending Balance, shares at Mar. 31, 2020				67,058,155
Beginning Balance at Dec. 31, 2020	2,756,737		$ 144,484	$ 141,834	1,634,815	831,688		(25,949)	31,359	(1,494)
Beginning Balance, shares at Dec. 31, 2020				67,254,706
Net income	73,115					73,115
Other comprehensive income (loss)	(21,556)								(21,556)
Comprehensive income	51,559
Common dividends declared	(22,095)					(22,095)
Preferred dividends declared ($16.875 per share)	(2,531)					(2,531)
Stock issued for dividend reinvestment						(391)		391
Stock issued for dividend reinvestment, shares				11,720
Treasury shares acquired					183			(183)
Treasury shares acquired, shares				(5,135)
Stock options exercised	569				(183)			752
Stock options exercised, shares				20,843
Stock compensation expense	1,288				1,288
Deferred benefits for directors- net	(5)									(5)
Ending Balance at Mar. 31, 2021	$ 2,785,522		$ 144,484	$ 141,834	$ 1,636,103	$ 879,786		$ (24,989)	$ 9,803	$ (1,499)
Ending Balance, shares at Mar. 31, 2021				67,282,134