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, 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	25,082		25,082
Other comprehensive income (loss), net of tax	8,024			8,024
Cash dividends declared	(8,767)		(8,767)
Treasury shares purchased under deferred directors' plan	0	$ 226			(226)
Treasury shares purchased under deferred directors' plan (in shares)		(7,613)
Stock activity under equity compensation plans	(143)	$ (143)
Stock activity under equity compensation plans (in shares)		82,775
Stock based compensation expense	1,796	$ 1,796
Balance at Jun. 30, 2016	418,804	$ 101,002	310,317	10,166	(2,681)
Balance (in shares) at Jun. 30, 2016		24,894,228
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
Comprehensive income:
Net income	29,878		29,878
Other comprehensive income (loss), net of tax	2,756			2,756
Cash dividends declared	(10,324)		(10,324)
Treasury shares purchased under deferred directors' plan	0	$ 256			(256)
Treasury shares purchased under deferred directors' plan (in shares)		(5,638)
Stock activity under equity compensation plans	(1,736)	$ (1,736)
Stock activity under equity compensation plans (in shares)		89,532
Stock based compensation expense	2,819	$ 2,819
Balance at Jun. 30, 2017	$ 450,371	$ 105,744	$ 347,427	$ 369	$ (3,169)
Balance (in shares) at Jun. 30, 2017		25,021,759