CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2013	$ 321,875	$ 93,249	$ 233,108	$ (2,494)	$ (1,988)
Balance (in shares) at Dec. 31, 2013		24,566,173
Comprehensive income:
Net income	43,805		43,805
Other comprehensive income (loss), net of tax	6,324			6,324
Comprehensive income (loss)	50,129
Cash dividends declared	(13,568)		(13,568)
Treasury shares purchased under deferred directors' plan	0	$ 444			(444)
Treasury shares purchased under deferred directors' plan (in shares)		(17,201)
Treasury stock sold and distributed under deferred directors' plan	0	$ (432)			432
Treasury stock sold and distributed under deferred directors' plan (in shares)		37,547
Stock activity under equity incentive plans	57	$ 57
Stock activity under equity incentive plans (in shares)		111,912
Stock based compensation expense	2,803	$ 2,803
Balance at Dec. 31, 2014	361,296	$ 96,121	263,345	3,830	(2,000)
Balance (in shares) at Dec. 31, 2014		24,698,431
Comprehensive income:
Net income	46,367		46,367
Other comprehensive income (loss), net of tax	(1,688)			(1,688)
Comprehensive income (loss)	44,679
Cash dividends declared	(15,710)		(15,710)
Treasury shares purchased under deferred directors' plan	0	$ 455			(455)
Treasury shares purchased under deferred directors' plan (in shares)		(16,356)
Stock activity under equity incentive plans	12	$ 12
Stock activity under equity incentive plans (in shares)		136,991
Stock based compensation expense	2,535	$ 2,535
Balance at Dec. 31, 2015	392,812	$ 99,123	294,002	2,142	(2,455)
Balance (in shares) at Dec. 31, 2015		24,819,066
Comprehensive income:
Net income	52,084		52,084
Other comprehensive income (loss), net of tax	(4,529)			(4,529)
Comprehensive income (loss)	47,555
Cash dividends declared	(18,213)		(18,213)
Treasury shares purchased under deferred directors' plan	0	$ 458			(458)
Treasury shares purchased under deferred directors' plan (in shares)		(14,811)
Stock activity under equity incentive plans	614	$ 614
Stock activity under equity incentive plans (in shares)		133,646
Stock based compensation expense	4,210	$ 4,210
Fractional shares retired due to 3-for-2 stock split (in shares)		(36)
Balance at Dec. 31, 2016	$ 426,978	$ 104,405	$ 327,873	$ (2,387)	$ (2,913)
Balance (in shares) at Dec. 31, 2016		24,937,865