Derivative Instruments (Details 1) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Fair value and notional amount of derivative instrument
Derivative, Notional Amount	$ 1,215,243	$ 1,322,956
Interest Rate Contracts [Member]
Fair value and notional amount of derivative instrument
Derivative, Notional Amount	1,180,562	1,287,399
Interest Rate Contracts [Member] | Other Assets [Member]
Fair value and notional amount of derivative instrument
Derivative Asset, Fair Value	45,876	41,309
Interest Rate Contracts [Member] | Other Liabilities [Member]
Fair value and notional amount of derivative instrument
Derivative Liability, Fair Value	77,257	77,410
Foreign Exchange Contracts [Member]
Fair value and notional amount of derivative instrument
Derivative, Notional Amount	34,681	35,557
Foreign Exchange Contracts [Member] | Other Assets [Member]
Fair value and notional amount of derivative instrument
Derivative Asset, Fair Value	44	0
Foreign Exchange Contracts [Member] | Other Liabilities [Member]
Fair value and notional amount of derivative instrument
Derivative Liability, Fair Value	927	877
Other Assets [Member]
Fair value and notional amount of derivative instrument
Derivative Asset, Fair Value	45,920	41,309
Other Liabilities [Member]
Fair value and notional amount of derivative instrument
Derivative Liability, Fair Value	$ 78,184	$ 78,287