Loans - Consumer, Excluding Credit Card Loan Portfolio, Financial Effects of Modifications and Redefaults (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) loan_payment	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Financing Receivable, Impaired [Line Items]
Number of years before payment default under a modified loan	1 year
Carrying value	$ 844,195	$ 756,971	$ 832,792
Consumer, excluding credit card
Financing Receivable, Impaired [Line Items]
Carrying value	353,871	$ 304,917	344,355
Consumer, excluding credit card | In Process of Active or Suspended Foreclosure
Financing Receivable, Impaired [Line Items]
Carrying value	$ 1,100		1,200
Consumer, excluding credit card | Permanent Modification
Financing Receivable, Impaired [Line Items]
Weighted-average interest rate of loans with interest rate reductions – before TDR	5.28%	5.68%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.64%	2.64%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	21 years	23 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	$ 2	$ 3
Principal deferred	18	24
Principal forgiven	15	20
Balance of loans that redefaulted within one year of permanent modification	$ 36	$ 40
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	5.03%	5.42%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.42%	2.42%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	18 years	18 years
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – after TDR	38 years	33 years
Charge-offs recognized upon permanent modification	$ 1	$ 1
Principal deferred	8	6
Principal forgiven	3	1
Balance of loans that redefaulted within one year of permanent modification	$ 10	$ 5
Modifications, weighted-average remaining life	9 years
Consumer, excluding credit card | Residential Mortgage
Financing Receivable, Impaired [Line Items]
Carrying value	$ 176,106		166,239
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	5.51%	5.78%
Weighted-average interest rate of loans with interest rate reductions – after TDR	2.83%	2.74%
Weighted-average remaining contractual term (in years) of loans with term or payment extensions – before TDR	25 years	25 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	$ 1	$ 2
Principal deferred	10	18
Principal forgiven	12	19
Balance of loans that redefaulted within one year of permanent modification	26	$ 35
Consumer, excluding credit card | Business banking
Financing Receivable, Impaired [Line Items]
Carrying value	$ 21,370		21,208
Consumer, excluding credit card | Business banking | Maximum
Financing Receivable, Impaired [Line Items]
Number of years before payment default under a modified loan	1 year
Consumer, excluding credit card | Residential real estate
Financing Receivable, Impaired [Line Items]
Number of payments past due for deemed payment | loan_payment	2
Carrying value	$ 220,038		$ 211,798
Consumer, excluding credit card | Residential real estate | Maximum
Financing Receivable, Impaired [Line Items]
Number of months before a payment redefault under modified loans	12 months
Consumer, excluding credit card | Residential real estate | Permanent Modification
Financing Receivable, Impaired [Line Items]
Modifications, weighted-average remaining life	10 years