Loans Troubled Debt Restructurings (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) contracts	Jun. 30, 2014 USD ($) contracts	Jun. 30, 2015 USD ($) contracts	Jun. 30, 2014 USD ($) contracts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	95	197	224	366
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 4	$ 13	$ 12	$ 20
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	8	22	12	47
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 0	$ 4	$ 1	$ 5
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	19	40	55	89
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 3	$ 6	$ 9	$ 10
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	32	24	62	47
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 1	$ 2	$ 2	$ 3
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts		2		6
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $		$ 0		$ 0
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	0	0	1	5
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 0	$ 0	$ 0	$ 0
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts	32	46	71	89
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 0	$ 0	$ 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	4	63	23	83
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 0	$ 1	$ 0	$ 1