Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Derivative Financial Instruments
Liability derivatives, Fair value	$ 122,285	$ 117,920
Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	465,755	501,485
Asset derivatives, Fair value	10,984	16,346
Liability derivatives, Fair value	11,289	16,477
Interest rate swap contracts
Derivative Financial Instruments
Asset derivatives, Fair value	11,586	17,422
Liability derivatives, Fair value	11,794	17,740
Interest rate swap contracts | Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	445,258	446,024
Asset derivatives, Fair value	10,902	16,126
Liability derivatives, Fair value	11,110	16,444
Loan commitments | Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	8,497	33,961
Asset derivatives, Fair value	82	220
Forward contracts | Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	12,000	21,500
Liability derivatives, Fair value	$ 179	$ 33