Loans - Consumer, Excluding Credit Card Loan Portfolio, Financial Effects of Modifications and Redefaults (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) loan_payment	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Financing Receivable, Impaired [Line Items]
Number of years before payment default under a modified loan	1 year
Carrying value	$ 943,841	$ 925,611	$ 969,415
Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Carrying value	359,715	$ 373,243	373,637
Consumer, excluding credit card | In Process of Active or Suspended Foreclosure
Financing Receivable, Impaired [Line Items]
Carrying value	$ 654		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	$ 247,230		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	5.94%	5.11%
Weighted-average interest rate of loans with interest rate reductions – after TDR	4.00%	3.19%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	20 years	21 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	38 years	37 years
Charge-offs recognized upon permanent modification	$ 0	$ 1
Principal deferred	4	8
Principal forgiven	2	5
Balance of loans that redefaulted within one year of permanent modification	56	$ 38
Consumer, excluding credit card | Residential mortgage
Financing Receivable, Impaired [Line Items]
Carrying value	$ 220,158		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	6.63%	5.11%
Weighted-average interest rate of loans with interest rate reductions – after TDR	4.68%	3.45%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	21 years	24 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	38 years	36 years
Charge-offs recognized upon permanent modification	$ 0	$ 0
Principal deferred	3	6
Principal forgiven	1	3
Balance of loans that redefaulted within one year of permanent modification	$ 37	$ 23
Modifications, weighted-average remaining life	9 years
Consumer, excluding credit card | Home equity
Financing Receivable, Impaired [Line Items]
Carrying value	$ 27,072		$ 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	5.63%	5.11%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.70%	3.05%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	20 years	19 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	38 years	38 years
Charge-offs recognized upon permanent modification	$ 0	$ 1
Principal deferred	1	2
Principal forgiven	1	2
Balance of loans that redefaulted within one year of permanent modification	$ 19	$ 15
Modifications, weighted-average remaining life	9 years