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) Income [Member]	Deferred Benefits for Directors [Member]
Beginning Balance at Dec. 31, 2014	$ 788,190	$ 61,182	$ 244,661	$ 504,578	$ (2,151)	$ (18,825)	$ (1,255)
Beginning Balance, shares at Dec. 31, 2014		29,298,188
Net income	57,760			57,760
Other comprehensive income	4,379					4,379
Comprehensive income	62,139
Common dividends declared ($0.72 and $0.69 per share in September 30, 2016 and 2015 respectively)	(26,561)			(26,561)
Shares issued for acquisition	293,629	$ 19,122	274,507
Shares issued for acquisition, shares		9,178,531
Treasury shares acquired	(2,065)				(2,065)
Treasury shares acquired, shares		(64,102)
Stock options exercised	1,473		(295)		1,768
Stock options exercised, shares		55,375
Restricted stock granted			(1,558)		1,558
Restricted stock granted,Shares		49,550
Repurchase of stock warrant	(2,247)		(2,247)
Stock compensation expense	1,184		1,184
Deferred benefits for directors- net			(469)				469
Ending Balance at Sep. 30, 2015	1,115,742	$ 80,304	515,783	535,777	(890)	(14,446)	(786)
Ending Balance, shares at Sep. 30, 2015		38,517,542
Beginning Balance at Dec. 31, 2015	1,122,132	$ 80,304	516,294	549,921	(2,640)	(20,954)	(793)
Beginning Balance, shares at Dec. 31, 2015		38,459,635
Net income	62,417			62,417
Other comprehensive income	15,892					15,892
Comprehensive income	78,309
Common dividends declared ($0.72 and $0.69 per share in September 30, 2016 and 2015 respectively)	(28,946)			(28,946)
Shares issued for acquisition	177,149	$ 11,071	162,934		3,144
Shares issued for acquisition, shares		5,423,348
Treasury shares acquired	(3,674)		56		(3,730)
Treasury shares acquired, shares		(130,041)
Stock options exercised	792	$ 2	(165)		955
Stock options exercised, shares		31,541
Restricted stock granted			(2,271)		$ 2,271
Restricted stock granted,Shares		76,400
Stock compensation expense	1,389		1,389
Deferred benefits for directors- net			(230)				230
Ending Balance at Sep. 30, 2016	$ 1,347,151	$ 91,377	$ 678,007	$ 583,392		$ (5,062)	$ (563)
Ending Balance, shares at Sep. 30, 2016		43,860,883