Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	$ 457,435	$ 501,485
Asset derivatives, Fair value	11,657	16,346
Liability derivatives, Fair value	10,945	16,477
Interest rate swap contracts
Derivative Financial Instruments
Asset derivatives, Fair value	11,523	17,422
Liability derivatives, Fair value	11,728	17,740
Interest rate swap contracts | Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	423,397	446,024
Asset derivatives, Fair value	10,740	16,126
Liability derivatives, Fair value	10,945	16,444
Loan commitments | Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	14,438	33,961
Asset derivatives, Fair value	153	220
Forward contracts | Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	19,600	21,500
Asset derivatives, Fair value	764
Liability derivatives, Fair value		$ 33