CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balances at Dec. 31, 2012	$ 483,512	$ 24,905	$ 191,689	$ 255,606	$ 11,312
Net income	44,422	0	0	44,422	0
Other comprehensive loss, net of tax	(14,282)	0	0	0	(14,282)
Common stock dividends - $0.90, $0.76, and $0.64 per share at December 31, 2015, 2014, and 2013, respectively	(16,130)	0	0	(16,130)	0
Stock compensation expense	1,688	0	1,688	0	0
Common stock issued pursuant to:
Stock option plan - 39,787, 13,834, and 10,964shares at December 31, 2015, 2014, and 2013, respectively	139	11	128	0	0
Employee stock purchase plan - 25,136, 24,519, and 24,849 shares at December 31, 2015, 2014, and 2013, respectively	461	25	436	0	0
Restricted stock - 55,784, 54,535, and 48,816 shares at December 31, 2015, 2014, and 2013, respectively	(447)	49	(496)	0	0
Balances at Dec. 31, 2013	499,363	24,990	193,445	283,898	(2,970)
Net income	38,200	0	0	38,200	0
Other comprehensive loss, net of tax	2,147	0	0	0	2,147
Common stock dividends - $0.90, $0.76, and $0.64 per share at December 31, 2015, 2014, and 2013, respectively	(19,216)	0	0	(19,216)	0
Stock compensation expense	1,452
Stock compensation expense, Adjustments to Additional Paid in Capital, Requisite Service Period Recognition, Total	1,773	0	1,773	0	0
Common stock issued pursuant to:
Stock option plan - 39,787, 13,834, and 10,964shares at December 31, 2015, 2014, and 2013, respectively	190	14	176	0	0
Employee stock purchase plan - 25,136, 24,519, and 24,849 shares at December 31, 2015, 2014, and 2013, respectively	509	25	484	0	0
Restricted stock - 55,784, 54,535, and 48,816 shares at December 31, 2015, 2014, and 2013, respectively	(305)	54	(359)	0	0
Purchase of treasury shares - 870,450 and 38,032 shares at December 31, 2015 and 2014, respectively	(910)	(38)	(872)	0	0
Balances at Dec. 31, 2014	521,751	25,045	194,647	302,882	(823)
Net income	45,355	0	0	45,355	0
Other comprehensive loss, net of tax	(474)	0	0	0	(474)
Common stock dividends - $0.90, $0.76, and $0.64 per share at December 31, 2015, 2014, and 2013, respectively	(22,397)	0	0	(22,397)	0
Stock compensation expense	1,979	0	1,979	0	0
Common stock issued pursuant to:
Stock option plan - 39,787, 13,834, and 10,964shares at December 31, 2015, 2014, and 2013, respectively	602	40	562	0	0
Directors stock purchase plan - 837 shares at December 31, 2015.	22	1	21	0	0
Employee stock purchase plan - 25,136, 24,519, and 24,849 shares at December 31, 2015, 2014, and 2013, respectively	566	25	541	0	0
Restricted stock - 55,784, 54,535, and 48,816 shares at December 31, 2015, 2014, and 2013, respectively	(353)	56	(409)	0	0
Purchase of treasury shares - 870,450 and 38,032 shares at December 31, 2015 and 2014, respectively	(22,624)	(871)	(21,753)	0	0
Balances at Dec. 31, 2015	$ 524,427	$ 24,296	$ 175,588	$ 325,840	$ (1,297)