Loans Troubled Debt Restructurings (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) contracts	Dec. 31, 2014 USD ($) contracts	Dec. 31, 2013 USD ($) contracts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	552	678	975
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 25	$ 36	$ 48
Commercial and Industrial Sector [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	34	78	55
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 1	$ 10	$ 5
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts			5
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $			$ 3
Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts			1
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $			$ 0
Residential Nonguaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	120	158	287
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 16	$ 19	$ 23
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	138	101	188
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 6	$ 5	$ 10
Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts		6	48
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $		$ 0	$ 3
Consumer Other Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	5	9	15
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 0	$ 0	$ 1
Consumer Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	171	181	207
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 2	$ 1	$ 2
Credit Card Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Restructured, Payment Default During Peiriod, Number of Contracts | contracts	84	145	169
Financing Receivable, Restructured, Payment Default During Period, Amortized Cost at Default | $	$ 0	$ 1	$ 1