Loans - Consumer, Excluding Credit Card Loan Portfolio (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 844,195	$ 832,792	$ 756,971
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	43,932	45,559
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	353,871	344,355	$ 304,917
Consumer, excluding credit card | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	43,932	45,559
Consumer, excluding credit card | Home equity | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	14,522	14,989
Consumer, excluding credit card | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	176,106	166,239
Consumer, excluding credit card | Residential Mortgage | Prime mortgage | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	8,594	8,893
Consumer, excluding credit card | Residential Mortgage | Subprime mortgage | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	3,174	3,263
Consumer, excluding credit card | Residential Mortgage | Option ARMs | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	13,453	13,853
Consumer, excluding credit card | Auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	62,937	60,255
Consumer, excluding credit card | Business banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	21,370	21,208
Consumer, excluding credit card | Student and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 9,783	$ 10,096