Loans and Allowance for Loan Losses (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended					12 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Substandard [Member] D	Sep. 30, 2012 Loss And Charged Off [Member] D	Sep. 30, 2012 Accruing TDRs With Modifications And Renewals Completed [Member]	Dec. 31, 2011 Accruing TDRs With Modifications And Renewals Completed [Member]	Sep. 30, 2011 Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retail loan substandard period (in days)					90
Retail loan charge-off period (in days)						120
Accruing troubled debt restructuring	$ 698,800,000		$ 698,800,000
Provision for losses on loans	63,572,000	(102,325,000)	(173,843,000)	(364,230,000)			52,100,000	60,700,000
Allowance for loan losses allocated to accuring TDRs				668,500,000
Commercial-type impaired loans									$ 1,000,000