Loans - Consumer, Excluding Credit Card Loan Portfolio, Financial Effects of Modifications and Redefaults (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) loan_payment	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Financing Receivable, Impaired [Line Items]
Number of years before payment default under a modified loan			1 year
Carrying value	$ 947,728	$ 940,440	$ 947,728	$ 940,440	$ 969,415
Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Carrying value	351,692	$ 374,587	351,692	$ 374,587	373,637
Consumer, excluding credit card | In Process of Active or Suspended Foreclosure
Financing Receivable, Impaired [Line Items]
Carrying value	609		$ 609		653
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	$ 240,761		$ 240,761		259,418
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	5.76%	5.10%	5.86%	5.11%
Weighted-average interest rate of loans with interest rate reductions – after TDR	4.14%	3.24%	4.06%	3.21%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	19 years	23 years	20 years	22 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	39 years	38 years	39 years	38 years
Charge-offs recognized upon permanent modification	$ 1	$ 0	$ 1	$ 1
Principal deferred	7	7	11	15
Principal forgiven	2	5	4	10
Balance of loans that redefaulted within one year of permanent modification	39	$ 44	87	$ 78
Consumer, excluding credit card | Residential mortgage
Financing Receivable, Impaired [Line Items]
Carrying value	$ 214,744		$ 214,744		231,078
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	6.03%	4.97%	6.28%	5.03%
Weighted-average interest rate of loans with interest rate reductions – after TDR	4.47%	3.15%	4.56%	3.28%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	19 years	25 years	20 years	25 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	39 years	37 years	39 years	37 years
Charge-offs recognized upon permanent modification	$ 1	$ 0	$ 1	$ 0
Principal deferred	5	4	8	10
Principal forgiven	1	3	2	6
Balance of loans that redefaulted within one year of permanent modification	23	$ 25	$ 56	$ 45
Modifications, weighted-average remaining life			9 years
Consumer, excluding credit card | Home equity
Financing Receivable, Impaired [Line Items]
Carrying value	$ 26,017		$ 26,017		$ 28,340
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	5.51%	5.21%	5.59%	5.16%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.83%	3.31%	3.75%	3.16%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	20 years	18 years	20 years	19 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	40 years	37 years	40 years	39 years
Charge-offs recognized upon permanent modification	$ 0	$ 0	$ 0	$ 1
Principal deferred	2	3	3	5
Principal forgiven	1	2	2	4
Balance of loans that redefaulted within one year of permanent modification	$ 16	$ 19	$ 31	$ 33
Modifications, weighted-average remaining life			9 years