Loans - Consumer, Excluding Credit Card Loan Portfolio, Financial Effects of Modifications and Redefaults (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) loan_payment	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Financing Receivable, Impaired [Line Items]
Carrying value	$ 804,293	$ 735,304	$ 804,293	$ 735,304	$ 747,508
Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Carrying value	331,732	$ 288,379	331,732	$ 288,379	294,979
Consumer, excluding credit card | In Process of Active or Suspended Foreclosure
Financing Receivable, Impaired [Line Items]
Carrying value	1,200		1,200		1,500
Consumer, excluding credit card | Business banking
Financing Receivable, Impaired [Line Items]
Carrying value	20,871		$ 20,871		20,058
Consumer, excluding credit card | Residential real estate
Financing Receivable, Impaired [Line Items]
Number of payments past due for deemed payment | loan_payment			2
Carrying value	$ 201,097		$ 201,097		162,719
Permanent Modification | Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	5.57%	5.14%	5.57%	5.63%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.65%	2.87%	2.65%	2.79%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	22 years	22 years	22 years	23 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	36 years	35 years	36 years	36 years
Charge-offs recognized upon permanent modification	$ 5	$ 5	$ 12	$ 33
Principal deferred	20	15	65	57
Principal forgiven	19	109	54	189
Balance of loans that redefaulted within one year of permanent modification	43	$ 75	$ 116	$ 191
Maximum | Consumer, excluding credit card | Business banking
Financing Receivable, Impaired [Line Items]
Number of years before payment default under a modified loan			1 year
Maximum | Consumer, excluding credit card | Residential real estate
Financing Receivable, Impaired [Line Items]
Number of months before a payment redefault under modified loans			12 months
Prime, including option ARMs | Consumer, excluding credit card | Mortgages
Financing Receivable, Impaired [Line Items]
Carrying value	$ 150,114		$ 150,114		104,921
Prime, including option ARMs | Permanent Modification | Consumer, excluding credit card | Mortgages
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	5.07%	4.16%	5.08%	4.81%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.61%	2.77%	2.50%	2.70%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	25 years	25 years	25 years	25 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	36 years	37 years	37 years	37 years
Charge-offs recognized upon permanent modification	$ 4	$ 1	$ 7	$ 5
Principal deferred	9	8	31	31
Principal forgiven	10	51	26	76
Balance of loans that redefaulted within one year of permanent modification	23	$ 35	$ 58	$ 97
Modifications, weighted-average remaining life			10 years
Subprime | Consumer, excluding credit card | Mortgages
Financing Receivable, Impaired [Line Items]
Carrying value	$ 3,853		$ 3,853		$ 5,056
Subprime | Permanent Modification | Consumer, excluding credit card | Mortgages
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	6.82%	6.97%	6.73%	7.29%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.11%	3.45%	3.17%	3.44%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	24 years	22 years	24 years	24 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	37 years	35 years	36 years	36 years
Charge-offs recognized upon permanent modification	$ 0	$ 1	$ 2	$ 2
Principal deferred	4	4	14	15
Principal forgiven	9	49	26	81
Balance of loans that redefaulted within one year of permanent modification	$ 15	$ 32	$ 44	$ 72
Modifications, weighted-average remaining life			8 years
Senior lien | Permanent Modification | Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Modifications, weighted-average remaining life			10 years
Senior lien | Permanent Modification | Consumer, excluding credit card | Home equity
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	5.55%	6.05%	5.82%	6.45%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.61%	3.13%	2.74%	3.03%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	17 years	18 years	17 years	18 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	33 years	31 years	32 years	30 years
Charge-offs recognized upon permanent modification	$ 1	$ 1	$ 1	$ 2
Principal deferred	3	1	10	3
Principal forgiven	0	6	2	12
Balance of loans that redefaulted within one year of permanent modification	$ 4	$ 5	$ 10	$ 14
Junior lien | Permanent Modification | Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Modifications, weighted-average remaining life			9 years
Junior lien | Permanent Modification | Consumer, excluding credit card | Home equity
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	4.96%	4.81%	4.85%	4.83%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.15%	2.07%	2.20%	1.95%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	17 years	19 years	18 years	19 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	34 years	35 years	34 years	35 years
Charge-offs recognized upon permanent modification	$ 0	$ 2	$ 2	$ 24
Principal deferred	4	2	10	8
Principal forgiven	0	3	0	20
Balance of loans that redefaulted within one year of permanent modification	$ 1	$ 3	$ 4	$ 8