Loans Troubled Debt Restructurings (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) contracts	Sep. 30, 2014 USD ($) contracts	Sep. 30, 2015 USD ($) contracts	Sep. 30, 2014 USD ($) contracts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	142	212	366	578
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 5	$ 10	$ 18	$ 30
Commercial and Industrial Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	13	30	25	77
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 0	$ 3	$ 1	$ 8
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	25	46	80	135
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 3	$ 6	$ 12	$ 16
Home Equity Line of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	33	28	95	75
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 2	$ 1	$ 4	$ 4
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts		0		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 | contracts	2	3	3	8
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 | contracts	47	45	118	134
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 0	$ 0	$ 1	$ 1
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	22	60	45	143
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default	$ 0	$ 0	$ 0	$ 1