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 Income (Loss) [Member]
Common stock, shares outstanding, beginning balance at Dec. 31, 2012		16,380,000
Stockholders' equity, beginning balance at Dec. 31, 2012	$ 295,652	$ 1,024	$ 91,453	$ 213,674	$ (10,499)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	36,153			36,153
Total other comprehensive income (loss), net of tax	8,946				8,946
Cash dividends declared	(17,232)			(17,232)
Share-based compensation	1,876		1,876
Deferred compensation plan, shares		2,000
Deferred compensation plan	30	$ 0	30
Common stock issued for acquisition	0
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		232,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	4,221	$ 14	4,207
Common stock, shares outstanding, ending balance at Dec. 31, 2013		16,614,000
Stockholders' equity, ending balance at Dec. 31, 2013	329,646	$ 1,038	97,566	232,595	(1,553)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	40,824			40,824
Total other comprehensive income (loss), net of tax	(7,256)				(7,256)
Cash dividends declared	20,582			(20,582)
Share-based compensation	1,880		1,880
Common stock issued for acquisition	0
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		132,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	$ 1,767	$ 9	1,758
Common stock, shares outstanding, ending balance at Dec. 31, 2014	16,746,363	16,746,000
Stockholders' equity, ending balance at Dec. 31, 2014	$ 346,279	$ 1,047	101,204	252,837	(8,809)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	43,465			43,465
Total other comprehensive income (loss), net of tax	(890)				(890)
Cash dividends declared	23,228			(23,228)
Share-based compensation	2,074		2,074
Common stock issued for acquisition, shares		137,000
Common stock issued for acquisition	5,430	$ 8	5,422
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit, shares		137,000
Exercise of stock options, issuance of other compensation-related equity instruments and related tax benefit	$ 2,258	$ 9	2,249
Common stock, shares outstanding, ending balance at Dec. 31, 2015	17,019,578	17,020,000
Stockholders' equity, ending balance at Dec. 31, 2015	$ 375,388	$ 1,064	$ 110,949	$ 273,074	$ (9,699)