Loans Troubled Debt Restructurings (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 contracts	Mar. 31, 2012 contracts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	246	180
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 13	$ 19
Commercial and Industrial | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	23	11
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	0	2
Commercial Real Estate | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	1	4
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	3	4
Commercial Construction [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	1	3
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	0	2
Residential Nonguaranteed [Member] | Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	76	28
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	4	5
Home Equity | Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	49	43
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	3	3
Residential Construction | Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	6	11
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	1	2
Consumer Other Direct | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	7	2
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	0	0
Consumer Indirect | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	39
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	1
Consumer Credit Card | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	44	78
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 1	$ 1