Loans TDR Modifications (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) contracts	Mar. 31, 2017 USD ($) contracts
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	1,443	1,611
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 10	$ 6
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	99	124
Financing Receivable, Amount Restructured During Period	$ 109	$ 130
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	46	30
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 0	$ 0
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	56	41
Financing Receivable, Amount Restructured During Period	$ 56	$ 41
Residential Nonguaranteed [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	61	34
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 9	$ 4
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	8	2
Financing Receivable, Amount Restructured During Period	$ 17	$ 6
Home Equity Line of Credit [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	136	655
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 0	$ 1
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	13	66
Financing Receivable, Amount Restructured During Period	$ 13	$ 67
Consumer Other Direct [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	114	110
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 0	$ 0
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	1	1
Financing Receivable, Amount Restructured During Period	$ 1	$ 1
Consumer Indirect [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	778	547
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 0	$ 0
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	20	14
Financing Receivable, Amount Restructured During Period	$ 20	$ 14
Credit Card Receivable [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	308	235
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 1	$ 1
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	1	0
Financing Receivable, Amount Restructured During Period	$ 2	$ 1