Loans - Consumer, Excluding Credit Card Loan Portfolio (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 804,293	$ 747,508	$ 735,304
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	331,732	294,979	$ 288,379
Consumer, excluding credit card | Home equity | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	15,490	17,095
Consumer, excluding credit card | Home equity | Senior lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	15,156	16,367
Consumer, excluding credit card | Home equity | Junior lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	31,974	36,375
Consumer, excluding credit card | Home equity | Junior lien | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	12,269	13,851
Consumer, excluding credit card | Mortgages | Prime
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	150,114	104,921
Consumer, excluding credit card | Mortgages | Prime | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	9,196	10,220
Consumer, excluding credit card | Mortgages | Subprime
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	3,853	5,056
Consumer, excluding credit card | Mortgages | Subprime | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	3,329	3,673
Consumer, excluding credit card | Mortgages | Option ARMs | Residential real estate – PCI
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	14,221	15,708
Consumer, excluding credit card | Auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	57,174	54,536
Consumer, excluding credit card | Business banking
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	20,871	20,058
Consumer, excluding credit card | Student and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 10,354	$ 10,970