CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock Outstanding [Member]	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balances at Dec. 31, 2014	$ 521,751		$ 25,045	$ 194,647	$ 302,882	$ (823)
Net income	21,558		0	0	21,558	0
Other comprehensive loss, net of tax	231		0	0	0	231
Common stock dividends - $0.48 and $0.44 per share at June 30, 2016 and 2015, respectively	(11,041)		0	0	(11,041)	0
Stock compensation expense, Adjustments to Additional Paid in Capital, Requisite Service Period Recognition, Total	941		0	941	0	0
Common stock issued pursuant to:
Stock option plan - 28,941 and 26,695 shares at June 30, 2016 and 2015, respectively	391		26	365	0	0
Employee stock purchase plan - 12,471 and 12,613 shares at June 30, 2016 and 2015, respectively	276		12	264	0	0
Directors stock purchase plan - 258 and 837 shares at June 30, 2016 and 2015, respectively	22		1	21	0	0
Restricted stock - 49,648 and 52,924 shares at June 30, 2016 and 2015, respectively	(341)		53	(394)	0	0
Purchase of treasury shares - 512,459 and 575,472 shares at June 30, 2016 and 2015, respectively	(14,915)	$ (575)		(14,340)	0	0
Balances at Jun. 30, 2015	518,873		24,562	181,504	313,399	(592)
Balances at Dec. 31, 2015	524,427		24,296	175,588	325,840	(1,297)
Net income	21,460		0	0	21,460	0
Other comprehensive loss, net of tax	7,183		0	0	0	7,183
Common stock dividends - $0.48 and $0.44 per share at June 30, 2016 and 2015, respectively	(11,622)		0	0	(11,622)	0
Stock compensation expense, Adjustments to Additional Paid in Capital, Requisite Service Period Recognition, Total	992		0	992	0	0
Common stock issued pursuant to:
Stock option plan - 28,941 and 26,695 shares at June 30, 2016 and 2015, respectively	422		29	393	0	0
Employee stock purchase plan - 12,471 and 12,613 shares at June 30, 2016 and 2015, respectively	291		12	279	0	0
Directors stock purchase plan - 258 and 837 shares at June 30, 2016 and 2015, respectively	16		1	15	0	0
Restricted stock - 49,648 and 52,924 shares at June 30, 2016 and 2015, respectively	(417)		49	(466)	0	0
Purchase of treasury shares - 512,459 and 575,472 shares at June 30, 2016 and 2015, respectively	(13,273)	$ (512)		(12,761)	0	0
Balances at Jun. 30, 2016	$ 529,479		$ 23,875	$ 164,040	$ 335,678	$ 5,886