Consolidated Statements of Changes in Stockholders’ Equity (Unaudited) (USD $) In Thousands	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]	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance, beginning of period at Dec. 31, 2011				$ 315	$ 195,628	$ (7,355)	$ 223,510	$ 4,813
Repurchase of outstanding shares	(2,444)	(835)	(511)
Change in net unrealized gains (losses) on securities available for sale, net of taxes of approximately $15,482 and ($6,401) for the nine months ended September 30, 2013 and 2012, respectively								8,303	8,303
Amortization of actuarial losses, net of taxes of approximately ($405) and ($347) for the nine months ended September 30, 2013 and 2012, respectively								447	(447)
Amortization of prior service credits, net of taxes of approximately $15 and $10 for the nine month periods ended September 30, 2013 and 2012, respectively								(19)	19
OTTI charges included in income, net of taxes of approximately ($620) and ($339) for the nine months ended September 30, 2013 and 2012, respectively)								437
Reclassification adjustment for gains included in net income, net of tax of approximately $1,299 and $42 for the nine months ended September 30, 2013 and 2012, respectively								(54)	(54)
Net income							25,131		25,131
Cash dividends declared and paid on common shares ($0.39 per common share for the nine months ended September 30, 2013 and 2012, respectively)							(11,885)
Award of common shares released from Employee Benefit Trust (141,059 and 154,543 common shares for the nine months ended September 30, 2013 and 2012, respectively)					1,442
Shares issued upon vesting of restricted stock unit awards					317	1,686	(97)
Issuance upon exercise of stock options					160	1,665	(37)		835
Stock-based compensation activity, net					670
Stock-based income tax benefit					111
Balance, end of period at Sep. 30, 2012			(7,794)	315	198,328		236,622	13,927	441,398
Balance, beginning of period at Dec. 31, 2012				315	198,314	(10,257)	241,856	12,137	442,365
Repurchase of outstanding shares	(13,152)	(4,075)	(912)
Change in net unrealized gains (losses) on securities available for sale, net of taxes of approximately $15,482 and ($6,401) for the nine months ended September 30, 2013 and 2012, respectively								(19,947)	(19,947)
Amortization of actuarial losses, net of taxes of approximately ($405) and ($347) for the nine months ended September 30, 2013 and 2012, respectively								522	(522)
Amortization of prior service credits, net of taxes of approximately $15 and $10 for the nine month periods ended September 30, 2013 and 2012, respectively								(19)	19
OTTI charges included in income, net of taxes of approximately ($620) and ($339) for the nine months ended September 30, 2013 and 2012, respectively)								799
Reclassification adjustment for gains included in net income, net of tax of approximately $1,299 and $42 for the nine months ended September 30, 2013 and 2012, respectively								(1,673)	(1,673)
Net income							25,804		25,804
Cash dividends declared and paid on common shares ($0.39 per common share for the nine months ended September 30, 2013 and 2012, respectively)							(11,747)
Award of common shares released from Employee Benefit Trust (141,059 and 154,543 common shares for the nine months ended September 30, 2013 and 2012, respectively)					1,608
Shares issued upon vesting of restricted stock unit awards					161	2,338	(100)
Issuance upon exercise of stock options					849	4,262	(126)		4,074
Stock-based compensation activity, net					(284)
Stock-based income tax benefit					339
Balance, end of period at Sep. 30, 2013			$ (21,796)	$ 315	$ 200,987		$ 255,687	$ (8,181)	$ 427,012