Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Deferred Benefits for Directors [Member]
Beginning Balance at Dec. 31, 2013	$ 746,595	$ 61,182	$ 244,974	$ 460,351	$ (5,969)	$ (12,734)	$ (1,209)
Beginning Balance, shares at Dec. 31, 2013		29,175,236
Net income	69,974			69,974
Other comprehensive loss	(6,091)					(6,091)
Comprehensive income	63,883
Common dividends declared ($0.88, $0.92, and $0.96 per share for year ended December 31, 2014, 2015, and 2016 respectively)	(25,747)			(25,747)
Stock options exercised	2,167		(399)		2,566
Stock options exercised, shares		82,656
Restricted stock granted			(1,321)		1,321
Restricted stock granted,Shares		42,554
Treasury shares acquired	(20)		49		(69)
Treasury shares acquired, shares		(2,258)
Stock compensation expense	1,312		1,312
Deferred benefits for directors-net			46				(46)
Ending Balance at Dec. 31, 2014	788,190	$ 61,182	244,661	504,578	(2,151)	(18,825)	(1,255)
Ending Balance, shares at Dec. 31, 2014		29,298,188
Net income	80,762			80,762
Other comprehensive loss	(2,129)					(2,129)
Comprehensive income	78,633
Common dividends declared ($0.88, $0.92, and $0.96 per share for year ended December 31, 2014, 2015, and 2016 respectively)	(35,419)			(35,419)
Shares issued for acquisition	293,629	$ 19,122	274,507
Shares issued for acquisition, shares		9,178,531
Stock options exercised	1,601		(324)		1,925
Stock options exercised, shares		60,275
Restricted stock granted			(1,558)		1,558
Restricted stock granted,Shares		49,550
Repurchase of stock warrant	(2,247)		(2,247)
Treasury shares acquired	(3,921)		51		(3,972)
Treasury shares acquired, shares		(126,909)
Stock compensation expense	1,666		1,666
Deferred benefits for directors-net			(462)				462
Ending Balance at Dec. 31, 2015	1,122,132	$ 80,304	516,294	549,921	(2,640)	(20,954)	(793)
Ending Balance, shares at Dec. 31, 2015		38,459,635
Net income	86,635			86,635
Other comprehensive loss	(6,172)					(6,172)
Comprehensive income	80,463
Common dividends declared ($0.88, $0.92, and $0.96 per share for year ended December 31, 2014, 2015, and 2016 respectively)	(39,485)			(39,485)
Shares issued for acquisition	177,149	$ 11,071	162,934		3,144
Shares issued for acquisition, shares		5,423,348
Stock options exercised	$ 2,920	$ 139	1,707		1,074
Stock options exercised, shares	101,190	101,190
Restricted stock granted		$ 10	(2,281)		2,271
Restricted stock granted,Shares		81,220
Treasury shares acquired	$ (3,793)		56		$ (3,849)
Treasury shares acquired, shares		(133,678)
Stock compensation expense	2,022		2,022
Deferred benefits for directors-net			(225)				225
Ending Balance at Dec. 31, 2016	$ 1,341,408	$ 91,524	$ 680,507	$ 597,071		$ (27,126)	$ (568)
Ending Balance, shares at Dec. 31, 2016		43,931,715