Loans - Consumer, Excluding Credit Card Loans, Financial Effects of Modifications and Redefaults (Details) (Consumer, excluding credit card, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
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	6.11%	6.67%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.72%	3.02%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	18 years	18 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	31 years	31 years
Charge-offs recognized upon permanent modification	$ 0	$ 1
Principal deferred	3	1
Principal forgiven	1	3
Balance of loans that redefaulted within one year of permanent modification(a)	3	6
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	4.97%	4.75%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.21%	1.81%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	18 years	20 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	34 years	35 years
Charge-offs recognized upon permanent modification	1	14
Principal deferred	3	3
Principal forgiven	0	11
Balance of loans that redefaulted within one year of permanent modification(a)	2	3
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	5.03%	5.22%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.38%	2.76%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	25 years	24 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	38 years	37 years
Charge-offs recognized upon permanent modification	1	2
Principal deferred	11	13
Principal forgiven	9	17
Balance of loans that redefaulted within one year of permanent modification(a)	18	30
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	6.80%	7.57%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.22%	3.41%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	24 years	25 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	36 years	36 years
Charge-offs recognized upon permanent modification	1	1
Principal deferred	7	7
Principal forgiven	10	21
Balance of loans that redefaulted within one year of permanent modification(a)	17	18
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	5.68%	5.91%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.64%	2.77%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	23 years	23 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	36 years	36 years
Charge-offs recognized upon permanent modification	3	18
Principal deferred	24	24
Principal forgiven	20	52
Balance of loans that redefaulted within one year of permanent modification(a)	$ 40	$ 57
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