Commitments and Contingent Liabilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Future minimum lease commitments under non-cancelable operating leases
2013	$ 1,573,000
2014	905,000
2015	832,000
2016	895,000
2017	842,000
Thereafter	2,767,000
Rent expense, net of sublease income	1,795,000	1,804,000	1,940,000
Commitments to extend credit and standby letters of credit
Commitments and contingent liabilities
The amount of commitments made by the entity	401,100,000	332,200,000
Standby letters of credit
Commitments and contingent liabilities
The amount of commitments made by the entity	14,800,000	13,300,000
Standby letters of credit | Minimum
Commitments and contingent liabilities
Term of the guarantee agreements	1 year
Standby letters of credit | Maximum
Commitments and contingent liabilities
Term of the guarantee agreements	2 years
Agreements to guarantee performance of customers contracts
Future minimum lease commitments under non-cancelable operating leases
Expected payment required in an event of default on all contracts	$ 2,700,000
Agreements to guarantee performance of customers contracts | Minimum
Commitments and contingent liabilities
Term of the guarantee agreements	2 months
Agreements to guarantee performance of customers contracts | Maximum
Commitments and contingent liabilities
Term of the guarantee agreements	10 months