Loans and Allowance for Credit Losses Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Receivables [Abstract]
Impaired Financing Receivable, Average Recorded Investment	$ 375,177,000		$ 772,300,000	$ 607,700,000
Interest income on impaired loans	5,562,000	[1]	27,400,000	26,500,000
Commitments to lend additional funds to borrowers	$ 1,700,000		$ 1,600,000

[1] Effective April 1, 2011, all impaired loans, excluding certain accruing TDRs, were non-accrual loans.