Loans - Consumer, Excluding Credit Card Loan Portfolio, Financial Effects of Modifications and Redefaults (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) loan_payment	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Financing Receivable, Impaired [Line Items]
Number of years before payment default under a modified loan			1 year
Carrying value	$ 940,440	$ 899,576	$ 940,440	$ 899,576	$ 924,838
Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Carrying value	374,587	$ 365,115	374,587	$ 365,115	372,553
Consumer, excluding credit card | In Process of Active or Suspended Foreclosure
Financing Receivable, Impaired [Line Items]
Carrying value	763		$ 763		787
Consumer, excluding credit card | Maximum
Financing Receivable, Impaired [Line Items]
Number of years before payment default under a modified loan			1 year
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	$ 256,324		$ 256,324		249,946
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 | 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	5.10%	5.09%	5.11%	5.06%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.24%	2.79%	3.21%	2.74%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	23 years	25 years	22 years	24 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	38 years	38 years	38 years	38 years
Charge-offs recognized upon permanent modification	$ 0	$ 0	$ 1	$ 2
Principal deferred	7	6	15	14
Principal forgiven	5	9	10	16
Balance of loans that redefaulted within one year of permanent modification	44	$ 42	78	$ 79
Consumer, excluding credit card | Residential mortgage
Financing Receivable, Impaired [Line Items]
Carrying value	$ 225,864		$ 225,864		216,496
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	4.97%	5.13%	5.03%	5.25%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.15%	3.12%	3.28%	3.00%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	25 years	23 years	25 years	24 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	37 years	37 years	37 years	38 years
Charge-offs recognized upon permanent modification	$ 0	$ 0	$ 0	$ 1
Principal deferred	4	4	10	7
Principal forgiven	3	6	6	11
Balance of loans that redefaulted within one year of permanent modification	25	$ 30	$ 45	$ 58
Modifications, weighted-average remaining life			9 years
Consumer, excluding credit card | Home equity
Financing Receivable, Impaired [Line Items]
Carrying value	$ 30,460		$ 30,460		$ 33,450
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	5.21%	5.04%	5.16%	4.82%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.31%	2.39%	3.16%	2.42%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	18 years	26 years	19 years	23 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	37 years	38 years	39 years	39 years
Charge-offs recognized upon permanent modification	$ 0	$ 0	$ 1	$ 1
Principal deferred	3	2	5	7
Principal forgiven	2	3	4	5
Balance of loans that redefaulted within one year of permanent modification	$ 19	$ 12	$ 33	$ 21
Modifications, weighted-average remaining life			8 years