CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($)	Total	Common Stock Outstanding [Member]	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balances at Dec. 31, 2013	$ 499,363,000		$ 24,990,000	$ 193,445,000	$ 283,898,000	$ (2,970,000)
Net income	29,052,000		0	0	29,052,000	0
Other comprehensive loss, net of tax	6,602,000		0	0	0	6,602,000
Common stock dividends - $0.66 and $0.56 per share at September 30, 2015 and 2014, respectively	(14,154,000)		0	0	(14,154,000)	0
Stock compensation expense	1,101,000
Stock compensation expense	1,318,000		0	1,318,000	0	0
Common stock issued pursuant to:
Stock option plan - 35,039 and 13,834 shares at September 30, 2015 and 2014, respectively	190,000		14,000	176,000	0	0
Employee stock purchase plan - 19,377 and 18,404 shares at September 30, 2015 and 2014, respectively	383,000		18,000	365,000	0	0
Restricted stock - 53,746 and 54,535 shares at September 30, 2015 and 2014, respectively	(350,000)		55,000	(405,000)	0	0
Balances at Sep. 30, 2014	522,404,000		25,077,000	194,899,000	298,796,000	3,632,000
Balances at Dec. 31, 2014	521,751,000		25,045,000	194,647,000	302,882,000	(823,000)
Net income	32,553,000		0	0	32,553,000	0
Other comprehensive loss, net of tax	2,624,000		0	0	0	2,624,000
Common stock dividends - $0.66 and $0.56 per share at September 30, 2015 and 2014, respectively	(16,496,000)		0	0	(16,496,000)	0
Stock compensation expense	1,450,000		0	1,450,000	0	0
Common stock issued pursuant to:
Stock option plan - 35,039 and 13,834 shares at September 30, 2015 and 2014, respectively	509,000		35,000	474,000	0	0
Employee stock purchase plan - 837 shares at September 30, 2015.	22,000		1,000	21,000	0	0
Employee stock purchase plan - 19,377 and 18,404 shares at September 30, 2015 and 2014, respectively	431,000		19,000	412,000	0	0
Restricted stock - 53,746 and 54,535 shares at September 30, 2015 and 2014, respectively	(381,000)		54,000	(435,000)	0	0
Purchase of treasury shares - 728,932 shares at September 30, 2015.	(18,869,000)	$ (729,000)		(18,140,000)	0	0
Balances at Sep. 30, 2015	$ 523,594,000		$ 24,425,000	$ 178,429,000	$ 318,939,000	$ 1,801,000