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, 2014	$ 284,554	$ 91,332	$ 62,980	$ 181,851	$ (14,462)	$ (37,147)
Beginning balance, shares at Dec. 31, 2014		16,221,607
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	27,268	$ 0	0	27,268	0	0
Other comprehensive loss, net of income tax benefit	(2,246)	0	0	0	(2,246)	0
Cash dividends declared ($0.80 per share)	(15,673)	0	0	(15,673)	0	0
Stock issued under dividend reinvestment and employee stock purchase plans	2,434	$ 0	52	0	0	2,382
Stock issued under dividend reinvestment and employee stock purchase plans and other employee benefit programs, shares		123,391
Stock Issued During Period, Value, Acquisitions	76,666	$ 18,939	57,727	0	0	0
Stock Issued During Period, Shares, Acquisitions		3,787,866
Exercise of stock options	461	$ 0	(54)	0	0	515
Exercise of stock options, shares		27,999
Stock-based compensation	1,421	$ 0	1,421	0	0	0
Net tax benefit on stock-based compensation	31	0	31	0	0	0
Purchases of treasury stock	(13,342)	$ 0	0	0	0	(13,342)
Purchases of treasury stock, shares		(675,754)
Restricted stock awards granted, net of cancellations	0	$ 0	(877)	0	0	877
Restricted stock awards granted, net of cancellations, shares		45,821
Ending balance at Dec. 31, 2015	361,574	$ 110,271	121,280	193,446	(16,708)	(46,715)
Ending balance, shares at Dec. 31, 2015		19,530,930
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	19,505	$ 0	0	19,505	0	0
Other comprehensive loss, net of income tax benefit	(2,746)	0	0	0	(2,746)	0
Cash dividends declared ($0.80 per share)	(18,435)	0	0	(18,435)	0	0
Stock issued under dividend reinvestment and employee stock purchase plans	2,472	$ 0	59	0	0	2,413
Stock issued under dividend reinvestment and employee stock purchase plans and other employee benefit programs, shares		115,269
Stock Issued During Period, Value, Acquisitions	144,146	$ 34,288	109,858	0	0	0
Stock Issued During Period, Shares, Acquisitions		6,857,529
Exercise of stock options	4,968	$ 0	59	0	0	4,909
Exercise of stock options, shares		261,050
Stock-based compensation	2,084	$ 0	2,084	0	0	0
Purchases of treasury stock	(8,359)	$ 0	0	0	0	(8,359)
Purchases of treasury stock, shares		(328,271)
Restricted stock awards granted, net of cancellations	0	$ 0	(2,846)	0	0	2,846
Restricted stock awards granted, net of cancellations, shares		152,846
Ending balance at Dec. 31, 2016	505,209	$ 144,559	230,494	194,516	(19,454)	(44,906)
Ending balance, shares at Dec. 31, 2016		26,589,353
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	44,094	$ 0	0	44,094	0	0
Other comprehensive loss, net of income tax benefit	1,683	0	0	0	1,683	0
Cash dividends declared ($0.80 per share)	(21,849)	0	0	(21,849)	0	0
Stock issued under dividend reinvestment and employee stock purchase plans	2,413	$ 0	181	0	0	2,232
Stock issued under dividend reinvestment and employee stock purchase plans and other employee benefit programs, shares		82,694
Stock Issued During Period, Value, Acquisitions	70,501	$ 13,225	57,276	0	0	0
Stock Issued During Period, Shares, Acquisitions		2,645,000
Exercise of stock options	$ 1,676	$ 0	(119)	0	0	1,795
Exercise of stock options, shares	92,370	92,370
Stock-based compensation	$ 3,166	$ 0	3,166	0	0	0
Purchases of treasury stock	(3,519)	$ 0	0	0	0	(3,519)
Purchases of treasury stock, shares		(119,798)
Restricted stock awards granted, net of cancellations	0	$ 0	(865)	0	0	865
Restricted stock awards granted, net of cancellations, shares		45,240
Ending balance at Dec. 31, 2017	$ 603,374	$ 157,784	$ 290,133	$ 216,761	$ (17,771)	$ (43,533)
Ending balance, shares at Dec. 31, 2017	29,334,859	29,334,859