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	12,529	$ 0	0	12,529	0	0
Other comprehensive income, net of income tax	2,338	0	0	0	2,338	0
Cash dividends declared ($0.40 per share)	(7,819)	0	0	(7,819)	0	0
Stock issued under dividend reinvestment and employee stock purchase plans	1,231	$ 0	25	0	0	1,206
Stock issued under dividend reinvestment and employee stock purchase plans, shares		61,281
Exercise of stock options	414	$ 0	(8)	0	0	422
Exercise of stock options, shares		22,667
Repurchase of cancelled restricted stock awards	0	$ 0	241	0	0	(241)
Repurchase of cancelled restricted stock awards, shares		(14,250)
Stock-based compensation	944	$ 0	944	0	0	0
Purchases of treasury stock	(2,051)	$ 0	0	0	0	(2,051)
Purchases of treasury stock, shares		(101,250)
Restricted stock awards granted	0	$ 0	(1,083)	0	0	1,083
Restricted stock awards granted, shares		58,580
Ending balance at Jun. 30, 2016	369,160	$ 110,271	121,399	198,156	(14,370)	(46,296)
Ending balance, shares at Jun. 30, 2016		19,557,958
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	22,634	$ 0	0	22,634	0	0
Other comprehensive income, net of income tax	2,272	0	0	0	2,272	0
Cash dividends declared ($0.40 per share)	(10,652)	0	0	(10,652)	0	0
Stock issued under dividend reinvestment and employee stock purchase plans	1,229	$ 0	72	0	0	1,157
Stock issued under dividend reinvestment and employee stock purchase plans, shares		43,415
Exercise of stock options	$ 1,328	$ 0	(105)	0	0	1,433
Exercise of stock options, shares	73,870	73,870
Repurchase of cancelled restricted stock awards	$ 0	$ 0	271	0	0	(271)
Repurchase of cancelled restricted stock awards, shares		(14,000)
Stock-based compensation	1,708	$ 0	1,708	0	0	0
Purchases of treasury stock	(2,422)	$ 0	0	0	0	(2,422)
Purchases of treasury stock, shares		(83,970)
Restricted stock awards granted	0	$ 0	(1,151)	0	0	1,151
Restricted stock awards granted, shares		59,323
Ending balance at Jun. 30, 2017	$ 521,306	$ 144,559	$ 231,289	$ 206,498	$ (17,182)	$ (43,858)
Ending balance, shares at Jun. 30, 2017		26,667,991