Commitments and Contingencies - Off-balance Sheet Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Commitments to extend credit [Member]
Financial instruments representing credit risk:
Off-balance Sheet Risks, Amount, Liability	$ 480,686
Performance letters of credit [Member]
Financial instruments representing credit risk:
Off-balance Sheet Risks, Amount, Liability	28,027
Financial standby letters of credit [Member]
Financial instruments representing credit risk:
Off-balance Sheet Risks, Amount, Liability	20,682
Other letters of credit [Member]
Financial instruments representing credit risk:
Off-balance Sheet Risks, Amount, Liability	$ 197