Net Deferred Tax Asset and Income Taxes (Schedule of Gross Deferred Tax Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Gross deferred tax assets:
Allowance for loan losses	$ 11,037	$ 10,642
Defined benefit pension obligations	11,462	10,969
Losses on write-downs of securities to fair value	1,500	1,695
Deferred compensation	2,174	1,900
Deferred loan origination fees	1,432	1,203
Stock based compensation	1,555	868
Other	2,680	2,530
Gross deferred tax assets	31,840	29,807
Gross deferred tax liabilities:
Net unrealized gains on securities available for sale	(4,318)	(6,136)
Amortization of intangibles	(2,207)	(2,459)
Deferred loan origination costs	(3,176)	(2,885)
Other	(2,255)	(1,899)
Gross deferred tax liabilities	(11,956)	(13,379)
Net deferred tax asset	$ 19,884	$ 16,428