Consolidated Statements of Changes in Stockholders’ Equity (Unaudited) (USD $) In Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member] Outstanding Common Shares Repurchased [Member]	Treasury Stock [Member] Shares Repurchased To Fund Options Exercised [Member]	Treasury Stock [Member] Shares Repurchased To Satisfy Tax Obligations [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance, beginning of period at Dec. 31, 2012	$ 315	$ 198,314				$ (10,257)	$ 241,856	$ 12,137
Repurchase of outstanding shares			(301)	(637)	(653)
Change in net unrealized gains (losses) on securities available for sale, net of taxes of approximately ($4,237) and $2,013 for the three months ended March 31, 2014 and 2013, respectively								(2,594)	(4,203)
Amortization of actuarial losses, net of taxes of approximately ($112) and ($135) for the three months ended March 31, 2014 and 2013, respectively								174	(174)
Amortization of prior service credits, net of taxes of approximately $8 and $5 for the three months ended March 31, 2014 and 2013, respectively)								(6)	6
Reclassification adjustment for net gains included in net income, net of taxes of approximately $1,249 for the three months ended March 31, 2013								(1,609)
Net income							6,756		6,756
Cash dividends declared and paid on common shares ($0.15 and $0.13 per common share for the three months ended March 31, 2014 and 2013, respectively)							(3,973)
Award of common shares released from Employee Benefit Trust (126,650 and 133,656 common shares for the three months ended March 31, 2014 and 2013, respectively)		1,563
Shares issued upon vesting of restricted stock unit awards		78				1,983	(99)
Issuance upon exercise of stock options		55				691	(35)		637
Stock-based compensation activity, net		(120)
Stock-based income tax benefit		245
Balance, end of period at Mar. 31, 2013	315	200,135			(9,174)		244,505	8,102	443,883
Balance, beginning of period at Dec. 31, 2013	315	201,902				(22,053)	263,743	(11,375)	432,532
Repurchase of outstanding shares			(556)	(478)	(1,103)
Change in net unrealized gains (losses) on securities available for sale, net of taxes of approximately ($4,237) and $2,013 for the three months ended March 31, 2014 and 2013, respectively								5,360	5,360
Amortization of actuarial losses, net of taxes of approximately ($112) and ($135) for the three months ended March 31, 2014 and 2013, respectively								63	(63)
Amortization of prior service credits, net of taxes of approximately $8 and $5 for the three months ended March 31, 2014 and 2013, respectively)								(3)	3
Net income							10,296		10,296
Cash dividends declared and paid on common shares ($0.15 and $0.13 per common share for the three months ended March 31, 2014 and 2013, respectively)							(4,513)
Award of common shares released from Employee Benefit Trust (126,650 and 133,656 common shares for the three months ended March 31, 2014 and 2013, respectively)		1,929
Shares issued upon vesting of restricted stock unit awards		3				2,897	(389)
Issuance upon exercise of stock options		122				797	(44)		478
Stock-based compensation activity, net		(26)
Stock-based income tax benefit		675
Balance, end of period at Mar. 31, 2014	$ 315	$ 204,605			$ (20,496)		$ 269,093	$ (5,955)	$ 447,562