Loans - Consumer, Excluding Credit Card Loan Portfolio, Financial Effects of Modifications and Redefaults (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) loan_payment	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Financing Receivable, Impaired [Line Items]
Carrying value	$ 928,887	$ 947,651	$ 928,887	$ 947,651	$ 969,415
Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Carrying value	331,809	$ 375,958	331,809	$ 375,958	373,637
Consumer, excluding credit card | In Process of Active or Suspended Foreclosure
Financing Receivable, Impaired [Line Items]
Carrying value	546		$ 546		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	$ 222,410		$ 222,410		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	5.57%	5.89%	5.77%	5.39%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.58%	4.01%	3.90%	3.49%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	20 years	21 years	20 years	22 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	39 years	39 years	39 years	38 years
Charge-offs recognized upon permanent modification	$ 0	$ 0	$ 1	$ 1
Principal deferred	6	9	17	24
Principal forgiven	2	4	6	14
Balance of loans that redefaulted within one year of permanent modification	53	$ 46	132	$ 118
Consumer, excluding credit card | Residential mortgage
Financing Receivable, Impaired [Line Items]
Carrying value	$ 197,456		$ 197,456		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	5.68%	6.13%	6.08%	5.45%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.99%	4.23%	4.36%	3.64%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	21 years	22 years	21 years	24 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	39 years	39 years	39 years	38 years
Charge-offs recognized upon permanent modification	$ 0	$ 0	$ 1	$ 0
Principal deferred	5	7	13	17
Principal forgiven	1	3	3	9
Balance of loans that redefaulted within one year of permanent modification	36	$ 27	$ 87	$ 69
Modifications, weighted-average remaining life			10 years
Consumer, excluding credit card | Home equity
Financing Receivable, Impaired [Line Items]
Carrying value	$ 24,954		$ 24,954		$ 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	5.50%	5.69%	5.56%	5.34%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.30%	3.83%	3.60%	3.39%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	19 years	18 years	20 years	18 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	39 years	39 years	40 years	39 years
Charge-offs recognized upon permanent modification	$ 0	$ 0	$ 0	$ 1
Principal deferred	1	2	4	7
Principal forgiven	1	1	3	5
Balance of loans that redefaulted within one year of permanent modification	$ 17	$ 19	$ 45	$ 49
Modifications, weighted-average remaining life			9 years