Loans Troubled Debt Restructurings (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 contracts	Mar. 31, 2014 contracts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	129	169
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 8	$ 7
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	4	25
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	1	1
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	36	49
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	6	4
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	30	23
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	1	1
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts		4
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default		0
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	1	5
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	0	0
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	39	43
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	0	1
Consumer Credit Card Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	19	20
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 0	$ 0