Loans Troubled Debt Restructurings (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 contracts	Dec. 31, 2013 contracts	Dec. 31, 2012 contracts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	678	975	683
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 36	$ 48	$ 52
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	78	55	84
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	10	5	5
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts		5	9
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default		3	5
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts		1	10
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default		0	7
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	158	287	141
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	19	23	20
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	101	188	164
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	5	10	11
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	6	48	24
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	0	3	3
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	9	15	4
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	0	1	0
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	181	207	43
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	1	2	0
Consumer Credit Card Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	145	169	204
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 1	$ 1	$ 1