Loans TDR Modifications (Details) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2018 USD ($) contracts	[1]	Jun. 30, 2017 USD ($) contracts	[2]	Jun. 30, 2018 USD ($) contracts		Jun. 30, 2017 USD ($) contracts	[4]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	1,592		1,789		3,035	[3]	3,400
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 10		$ 8		$ 20	[3]	$ 13
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	92		122		186	[3]	203
Financing Receivable, Amount Restructured During Period	$ 102		$ 130		$ 206	[3]	$ 216
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	29		30		75	[3]	60
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 0		$ 0		$ 0	[3]	$ 0
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	29		38		84	[3]	39
Financing Receivable, Amount Restructured During Period	$ 29		$ 38		$ 84	[3]	$ 39
Residential Nonguaranteed [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	159		45		219	[3]	79
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 8		$ 7		$ 17	[3]	$ 11
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	32		2		38	[3]	4
Financing Receivable, Amount Restructured During Period	$ 40		$ 9		$ 55	[3]	$ 15
Home Equity Line of Credit [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	144		621		280	[3]	1,276
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 0		$ 0		$ 0	[3]	$ 0
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	12		61		24	[3]	124
Financing Receivable, Amount Restructured During Period	$ 12		$ 61		$ 24	[3]	$ 124
Residential Construction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts					3
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted					$ 0
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted					0
Financing Receivable, Amount Restructured During Period					$ 0
Consumer Other Direct [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	214		180		328	[3]	290
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 0		$ 0		$ 0	[3]	$ 0
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	3		2		5	[3]	4
Financing Receivable, Amount Restructured During Period	$ 3		$ 2		$ 5	[3]	$ 4
Consumer Indirect [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	617		750		1,395	[3]	1,297
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 0		$ 0		$ 0	[3]	$ 0
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	16		19		35	[3]	32
Financing Receivable, Amount Restructured During Period	$ 16		$ 19		$ 35	[3]	$ 32
Credit Card Receivable [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	426		163		734	[3]	398
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 2		$ 1		$ 3	[3]	$ 2
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	0		0		0	[3]	0
Financing Receivable, Amount Restructured During Period	$ 2		$ 1		$ 3	[3]	$ 2

[1] Includes loans modified under the terms of a TDR that were charged-off during the period

[2] Includes loans modified under the terms of a TDR that were charged-off during the period.

[3] Includes loans modified under the terms of a TDR that were charged-off during the period.

[4] Includes loans modified under the terms of a TDR that were charged-off during the period.