Loans TDR Modifications (Details) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2018 USD ($) contracts	[1]	Sep. 30, 2017 USD ($) contracts	[2]	Sep. 30, 2018 USD ($) contracts		Sep. 30, 2017 USD ($) contracts	[4]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	1,270		1,868		4,305	[3]	5,300
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 5		$ 27		$ 23	[3]	$ 40
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	50		75		207	[3]	322
Financing Receivable, Amount Restructured During Period	$ 55		$ 102		$ 230	[3]	$ 362
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	47		76		122	[3]	136
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 0		$ 2		$ 0	[3]	$ 2
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	16		7		75	[3]	86
Financing Receivable, Amount Restructured During Period	$ 16		$ 9		$ 75	[3]	$ 88
Residential Nonguaranteed [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	48		41		267	[3]	119
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 3		$ 6		$ 18	[3]	$ 17
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	7		4		46	[3]	8
Financing Receivable, Amount Restructured During Period	$ 10		$ 10		$ 64	[3]	$ 25
Home Equity Line of Credit [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	130		696		410	[3]	1,971
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 1		$ 18		$ 1	[3]	$ 18
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	11		45		34	[3]	172
Financing Receivable, Amount Restructured During Period	$ 12		$ 63		$ 35	[3]	$ 190
Residential Construction [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts					4
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	141		135		469	[3]	425
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	2		2		6	[3]	6
Financing Receivable, Amount Restructured During Period	$ 2		$ 2		$ 6	[3]	$ 6
Consumer Indirect [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	559		738		1,954	[3]	2,034
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	14		17		46	[3]	50
Financing Receivable, Amount Restructured During Period	$ 14		$ 17		$ 46	[3]	$ 50
Credit Card Receivable [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Restructured During Period, Number Of Contracts | contracts	345		182		1,079	[3]	615
Financing Receivable, Amount Restructured During Period, Rate Modifications Granted	$ 1		$ 1		$ 4	[3]	$ 3
Financing Receivable, Amount Restructured During Period, Term Extension and/or Other Concessions Granted	0		0		0	[3]	0
Financing Receivable, Amount Restructured During Period	$ 1		$ 1		$ 4	[3]	$ 3

[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.