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	27,884					27,884
Other comprehensive income (loss)	39,315								39,315
Comprehensive income	67,199
Common dividends declared	$ (42,997)					(42,997)
Accounting Standards Update [Extensible List]	ASU 2016-13 [Member]
Treasury shares acquired	$ (25,227)				117			(25,344)
Treasury shares acquired, shares				(809,899)
Stock options exercised	445				(276)			721
Stock options exercised, shares				19,739
Restricted stock granted					(6,568)			6,568
Restricted stock granted, shares				176,924
Stock compensation expense	2,727				2,727
Deferred benefits for directors- net	44				113					(69)
Ending Balance at Jun. 30, 2020	2,569,521			$ 141,827	1,633,079	782,990		(27,518)	40,516	(1,373)
Ending Balance, shares at Jun. 30, 2020				67,211,192
Beginning Balance at Mar. 31, 2020	2,586,060			$ 141,827	1,638,122	800,064		(33,714)	41,141	(1,380)
Beginning Balance, shares at Mar. 31, 2020				67,058,155
Net income	4,488					4,488
Other comprehensive income (loss)	(625)								(625)
Comprehensive income	3,863
Common dividends declared	(21,562)					(21,562)
Treasury shares acquired	(255)				117			(372)
Treasury shares acquired, shares				(23,887)
Restricted stock granted					(6,568)			6,568
Restricted stock granted, shares				176,924
Stock compensation expense	1,357				1,357
Deferred benefits for directors- net	58				51					7
Ending Balance at Jun. 30, 2020	2,569,521			$ 141,827	1,633,079	782,990		(27,518)	40,516	(1,373)
Ending Balance, shares at Jun. 30, 2020				67,211,192
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	143,704					143,704
Other comprehensive income (loss)	(18,773)								(18,773)
Comprehensive income	124,931
Common dividends declared	(43,961)					(43,961)
Preferred dividends declared ($16.875 per share)	(5,063)					(5,063)
Stock issued for dividend reinvestment						(391)		391
Stock issued for dividend reinvestment, shares				11,720
Treasury shares acquired	(56,660)				191			(56,851)
Treasury shares acquired, shares				(1,510,576)
Stock options exercised	2,283				(858)			3,141
Stock options exercised, shares				91,643
Restricted stock granted					(4,272)			4,272
Restricted stock granted, shares				122,656
Stock compensation expense	2,580				2,580
Deferred benefits for directors- net	(11)				4					(15)
Ending Balance at Jun. 30, 2021	2,780,836		144,484	$ 141,834	1,632,460	925,977		(74,996)	12,586	(1,509)
Ending Balance, shares at Jun. 30, 2021				65,970,149
Beginning Balance at Mar. 31, 2021	2,785,522		144,484	$ 141,834	1,636,103	879,786		(24,989)	9,803	(1,499)
Beginning Balance, shares at Mar. 31, 2021				67,282,134
Net income	70,588					70,588
Other comprehensive income (loss)	2,783								2,783
Comprehensive income	73,371
Common dividends declared	(21,866)					(21,866)
Preferred dividends declared ($16.875 per share)	(2,531)					(2,531)
Treasury shares acquired	(56,661)				7			(56,668)
Treasury shares acquired, shares				(1,505,441)
Stock options exercised	1,715				(674)			2,389
Stock options exercised, shares				70,800
Restricted stock granted					(4,272)			4,272
Restricted stock granted, shares				122,656
Stock compensation expense	1,292				1,292
Deferred benefits for directors- net	(6)				4					(10)
Ending Balance at Jun. 30, 2021	$ 2,780,836		$ 144,484	$ 141,834	$ 1,632,460	$ 925,977		$ (74,996)	$ 12,586	$ (1,509)
Ending Balance, shares at Jun. 30, 2021				65,970,149