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	32,553		0	0	32,553	0
Other comprehensive loss, net of tax	2,624		0	0	0	2,624
Common stock dividends - $0.72 and $0.66 per share at September 30, 2016 and 2015, respectively	(16,496)		0	0	(16,496)	0
Stock compensation expense, Adjustments to Additional Paid in Capital, Requisite Service Period Recognition, Total	1,450		0	1,450	0	0
Common stock issued pursuant to:
Stock option plan - 34,646 and 35,039 shares at September 30, 2016 and 2015, respectively	509		35	474	0	0
Employee stock purchase plan - 18,767 and 19,377 shares at September 30, 2016 and 2015, respectively	431		19	412	0	0
Directors stock purchase plan - 258 and 837 shares at September 30, 2016 and 2015, respectively	22		1	21	0	0
Restricted stock - 49,648 and 53,746 shares at September 30, 2016 and 2015, respectively	(381)		54	(435)	0	0
Purchase of treasury shares - 512,459 and 728,932 shares at September 30, 2016 and 2015, respectively	(18,869)	$ (729)		(18,140)	0	0
Balances at Sep. 30, 2015	523,594		24,425	178,429	318,939	1,801
Balances at Dec. 31, 2015	524,427		24,296	175,588	325,840	(1,297)
Net income	34,934		0	0	34,934	0
Other comprehensive loss, net of tax	5,762		0	0	0	5,762
Common stock dividends - $0.72 and $0.66 per share at September 30, 2016 and 2015, respectively	(17,408)		0	0	(17,408)	0
Stock compensation expense, Adjustments to Additional Paid in Capital, Requisite Service Period Recognition, Total	1,628		0	1,628	0	0
Common stock issued pursuant to:
Stock option plan - 34,646 and 35,039 shares at September 30, 2016 and 2015, respectively	535		35	500	0	0
Employee stock purchase plan - 18,767 and 19,377 shares at September 30, 2016 and 2015, respectively	452		19	433	0	0
Directors stock purchase plan - 258 and 837 shares at September 30, 2016 and 2015, respectively	15		0	15	0	0
Restricted stock - 49,648 and 53,746 shares at September 30, 2016 and 2015, respectively	(417)		49	(466)	0	0
Purchase of treasury shares - 512,459 and 728,932 shares at September 30, 2016 and 2015, respectively	(13,273)	$ (512)		(12,761)	0	0
Balances at Sep. 30, 2016	$ 536,655		$ 23,887	$ 164,937	$ 343,366	$ 4,465