Commitments, Credit Risk And Contingencies (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Percentage of commitments to extend credit dependent upon the financial condition of the customer	82.10%
Commitments To Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Extended credit and standby letters of credit	$ 2,149,312	$ 1,943,889
Standby Letters Of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Extended credit and standby letters of credit	$ 109,204	$ 113,268