CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - UNAUDITED - USD ($) $ in Thousands	Total	Common Stock Outstanding [Member]	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance at 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 income, net of tax	5,762		0	0	0	5,762
Common stock dividends - $0.78 and $0.72 per share at September 30, 2017 and 2016 respectively.	(17,408)		0	0	(17,408)	0
Stock compensation expense	1,628		0	1,628	0	0
Common stock issued pursuant to:
Stock option plan - 28,736 and 34,646 shares at September 30, 2017 and 2016, respectively	535		35	500	0	0
Employee stock purchase plan - 13,486 and 18,767 shares at September 30, 2017 and 2016, respectively	452		19	433
Director's stock purchase plan - 258 shares at September 30, 2016	15		0	15
Restricted stock - 47,064 and 49, 648 shares at September 30, 2017 and 2016, respectively	(417)		49	(466)	0	0
Purchase of treasury shares - 512,459 shares at September 30, 2016	(13,273)	$ (512)		(12,761)	0	0
Balance at at Sep. 30, 2016	536,655		23,887	164,937	343,366	4,465
Balance at at Dec. 31, 2016	533,572		23,901	165,871	350,414	(6,614)
Net income	44,942		0	0	44,942	0
Other comprehensive income, net of tax	3,137		0	0	0	3,137
Common stock dividends - $0.78 and $0.72 per share at September 30, 2017 and 2016 respectively.	(18,844)		0	0	(18,844)	0
Stock compensation expense	1,611		0	1,611	0	0
Common stock issued pursuant to:
Stock option plan - 28,736 and 34,646 shares at September 30, 2017 and 2016, respectively	550		29	521	0	0
Employee stock purchase plan - 13,486 and 18,767 shares at September 30, 2017 and 2016, respectively	465		13	452	0	0
Restricted stock - 47,064 and 49, 648 shares at September 30, 2017 and 2016, respectively	(953)		47	(1,000)	0	0
Balance at at Sep. 30, 2017	$ 564,480		$ 23,990	$ 167,455	$ 376,512	$ (3,477)