Loans - Consumer, Excluding Credit Card Loans, Financial Effects of Modifications and Redefaults (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) loan_payment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Financing Receivable, Impaired [Line Items]
Carrying value	$ 889,907	$ 832,792	$ 747,508
Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Carrying value	364,406	344,355	$ 294,979
Consumer, excluding credit card | In the process of active or suspended foreclosure
Financing Receivable, Impaired [Line Items]
Carrying value	932	1,200
Consumer, excluding credit card | Home equity
Financing Receivable, Impaired [Line Items]
Carrying value	$ 39,063	$ 45,559
Consumer, excluding credit card | Home equity | Permanent Modification
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	4.99%	5.20%	5.27%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.34%	2.35%	2.30%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	18 years	18 years	19 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	38 years	35 years	33 years
Charge-offs recognized upon permanent modification	$ 1	$ 4	$ 27
Principal deferred	23	27	16
Principal forgiven	7	6	35
Balance of loans that redefaulted within one year of permanent modification	$ 40	21	$ 29
Modifications, weighted-average remaining life	9 years
Consumer, excluding credit card | Residential mortgage
Financing Receivable, Impaired [Line Items]
Carrying value	$ 192,163	$ 166,239
Consumer, excluding credit card | Residential mortgage | Permanent Modification
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	5.59%	5.67%	5.74%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.93%	2.79%	2.96%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	24 years	25 years	24 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	38 years	37 years	36 years
Charge-offs recognized upon permanent modification	$ 4	$ 11	$ 12
Principal deferred	30	58	58
Principal forgiven	44	66	172
Balance of loans that redefaulted within one year of permanent modification	$ 98	133	$ 214
Modifications, weighted-average remaining life	10 years
Consumer, excluding credit card | Total residential real estate – excluding PCI
Financing Receivable, Impaired [Line Items]
Number of payments past due for deemed payment | loan_payment	2
Carrying value	$ 231,226	$ 211,798
Consumer, excluding credit card | Total residential real estate – excluding PCI | Permanent Modification
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	5.36%	5.51%	5.61%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.70%	2.64%	2.78%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	22 years	22 years	23 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	38 years	36 years	36 years
Charge-offs recognized upon permanent modification	$ 5	$ 15	$ 39
Principal deferred	53	85	74
Principal forgiven	51	72	207
Balance of loans that redefaulted within one year of permanent modification	$ 138	154	$ 243
Consumer, excluding credit card | Total residential real estate – excluding PCI | Maximum
Financing Receivable, Impaired [Line Items]
Number of months before a payment redefault under modified loans	12 months
Consumer, excluding credit card | Business banking
Financing Receivable, Impaired [Line Items]
Carrying value	$ 22,698	$ 21,208
Consumer, excluding credit card | Business banking | Maximum
Financing Receivable, Impaired [Line Items]
Number of years before payment default under a modified loan	1 year