Commitments and Contingencies (Schedule of Remaining Contractual Loan Commitments by Class) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loan Commitments	$ 4,068,910	$ 4,151,541	$ 4,159,112
Commercial Loan [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loan Commitments	2,317,997	2,431,023	2,534,452
Consumer Loan [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Loan Commitments	$ 1,750,913	$ 1,720,518	$ 1,624,660