Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Treasury Stock [Member]
Beginning balance at Dec. 31, 2015	$ 361,574	$ 110,271	$ 121,280	$ 193,446	$ (16,708)	$ (46,715)
Beginning balance, shares at Dec. 31, 2015		19,530,930
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	12,587	$ 0	0	12,587	0	0
Other comprehensive income, net of income tax	2,504	0	0	0	2,504	0
Cash dividends declared ($0.60 per share)	(13,125)	0	0	(13,125)	0	0
Stock issued under dividend reinvestment and employee stock purchase plans	1,848	$ 0	42	0	0	1,806
Stock issued under dividend reinvestment and employee stock purchase plans, shares		90,420
Issuance of common stock, acquisition	144,146	$ 34,288	109,858	0	0	0
Issuance of common stock, acquisition, shares		6,857,529
Exercise of stock options	737	$ 0	(2)	0	0	739
Exercise of stock options, shares		39,829
Stock-based compensation	1,407	$ 0	1,407	0	0	0
Purchases of treasury stock	(2,429)	$ 0	0	0	0	(2,429)
Purchases of treasury stock, shares		(118,412)
Restricted stock awards granted, net of cancellations	0	$ 0	(2,950)	0	0	2,950
Restricted stock awards granted, net of cancellations, shares		158,116
Ending balance at Sep. 30, 2016	509,249	$ 144,559	229,635	192,908	(14,204)	(43,649)
Ending balance, shares at Sep. 30, 2016		26,558,412
Beginning balance at Dec. 31, 2016	505,209	$ 144,559	230,494	194,516	(19,454)	(44,906)
Beginning balance, shares at Dec. 31, 2016		26,589,353
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	33,830	$ 0	0	33,830	0	0
Other comprehensive income, net of income tax	3,111	0	0	0	3,111	0
Cash dividends declared ($0.60 per share)	(15,983)	0	0	(15,983)	0	0
Stock issued under dividend reinvestment and employee stock purchase plans	1,839	$ 0	130	0	0	1,709
Stock issued under dividend reinvestment and employee stock purchase plans, shares		63,683
Exercise of stock options	$ 1,527	$ 0	(121)	0	0	1,648
Exercise of stock options, shares	84,870	84,870
Stock-based compensation	$ 2,550	$ 0	2,550	0	0	0
Purchases of treasury stock	(3,285)	$ 0	0	0	0	(3,285)
Purchases of treasury stock, shares		(112,393)
Restricted stock awards granted, net of cancellations	0	$ 0	(881)	0	0	881
Restricted stock awards granted, net of cancellations, shares		45,823
Ending balance at Sep. 30, 2017	$ 528,798	$ 144,559	$ 232,172	$ 212,363	$ (16,343)	$ (43,953)
Ending balance, shares at Sep. 30, 2017		26,671,336