Loans - Consumer, Excluding Credit Card Loans, Financial Effects of Modifications and Redefaults (Details) (Consumer, excluding credit card, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business banking
Financing Receivable, Impaired [Line Items]
Balance of loans that redefaulted within one year of permanent modification(a)	$ 25	$ 43	$ 42
Number of years before payment default under a modified loan	1 year
Residential mortgage
Financing Receivable, Impaired [Line Items]
Number of payments past due for deemed payment	2
Permanent Modification | Home equity - senior lien
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	6.38%	6.35%	7.20%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.03%	3.23%	4.61%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	17 years	19 years	18 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	30 years	31 years	28 years
Charge-offs recognized upon permanent modification	2	7	8
Principal deferred	5	7	4
Principal forgiven	14	30	20
Balance of loans that redefaulted within one year of permanent modification(a)	19	26	30
Modifications, weighted-average remaining life	6 years
Permanent Modification | Home equity - junior lien
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	4.81%	5.05%	5.45%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.00%	2.14%	1.94%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	19 years	20 years	20 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	35 years	34 years	32 years
Charge-offs recognized upon permanent modification	25	70	65
Principal deferred	11	24	23
Principal forgiven	21	51	58
Balance of loans that redefaulted within one year of permanent modification(a)	10	20	46
Modifications, weighted-average remaining life	8 years
Permanent Modification | Mortgages - prime, including option ARMS
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	4.82%	5.28%	6.14%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.69%	2.77%	3.67%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	25 years	25 years	25 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	37 years	37 years	36 years
Charge-offs recognized upon permanent modification	9	16	35
Principal deferred	39	129	133
Principal forgiven	83	206	249
Balance of loans that redefaulted within one year of permanent modification(a)	121	164	255
Modifications, weighted-average remaining life	9 years
Permanent Modification | Mortgages - subprime
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	7.16%	7.33%	7.73%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.37%	3.52%	4.14%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	24 years	24 years	24 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	36 years	35 years	32 years
Charge-offs recognized upon permanent modification	3	5	29
Principal deferred	19	43	43
Principal forgiven	89	218	324
Balance of loans that redefaulted within one year of permanent modification(a)	93	106	156
Modifications, weighted-average remaining life	8 years
Permanent Modification | Residential real estate – excluding PCI
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	5.61%	5.88%	6.57%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.78%	2.92%	3.69%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	23 years	23 years	24 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	36 years	36 years	34 years
Charge-offs recognized upon permanent modification	39	98	137
Principal deferred	74	203	203
Principal forgiven	207	505	651
Balance of loans that redefaulted within one year of permanent modification(a)	$ 243	$ 316	$ 487
Maximum | Residential real estate – excluding PCI
Financing Receivable, Impaired [Line Items]
Number of months before a payment redefault under modified loans	12 months
Maximum | Business banking
Financing Receivable, Impaired [Line Items]
Number of years before payment default under a modified loan	1 year