Loans - Consumer, Excluding Credit Card Loans, Financial Effects of Modifications and Redefaults (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) loan_payment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Financing Receivable, Impaired [Line Items]
Carrying value	$ 969,415	$ 924,838	$ 889,907
Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Carrying value	373,637	372,553	$ 364,406
Consumer, excluding credit card | In the process of active or suspended foreclosure
Financing Receivable, Impaired [Line Items]
Carrying value	$ 653	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 | Residential mortgage
Financing Receivable, Impaired [Line Items]
Carrying value	$ 231,078	$ 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	5.65%	5.15%	5.59%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.80%	2.99%	2.93%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	24 years	24 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
Charge-offs recognized upon permanent modification	$ 1	$ 2	$ 4
Principal deferred	21	12	30
Principal forgiven	10	20	44
Balance of loans that redefaulted within one year of permanent modification	$ 97	124	$ 98
Modifications, weighted-average remaining life	9 years
Consumer, excluding credit card | Home equity
Financing Receivable, Impaired [Line Items]
Carrying value	$ 28,340	$ 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	5.39%	4.94%	4.99%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.46%	2.64%	2.34%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	19 years	21 years	18 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	39 years	39 years	38 years
Charge-offs recognized upon permanent modification	$ 1	$ 1	$ 1
Principal deferred	9	10	23
Principal forgiven	7	13	7
Balance of loans that redefaulted within one year of permanent modification	$ 64	56	$ 40
Modifications, weighted-average remaining life	8 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	$ 259,418	$ 249,946
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	5.50%	5.06%	5.36%
Weighted-average interest rate of loans with interest rate reductions – after TDR	3.60%	2.83%	2.70%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	21 years	23 years	22 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	38 years	38 years	38 years
Charge-offs recognized upon permanent modification	$ 2	$ 3	$ 5
Principal deferred	30	22	53
Principal forgiven	17	33	51
Balance of loans that redefaulted within one year of permanent modification	$ 161	$ 180	$ 138
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