Loans - Consumer, Excluding Credit Card Loan Portfolio, Delinquency Statistics Junior Lien Home Equity Loans (Details) - USD ($) $ in Millions	9 Months Ended
	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 | Junior lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 31,974	$ 36,375
% of 30 days past due to total retained loans	2.14%	2.20%
Consumer, excluding credit card | HELOANs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 2,582	$ 3,144
% of 30 days past due to total retained loans	2.75%	3.34%
Consumer, excluding credit card | HELOCs, Within the revolving period | HELOCs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 18,883	$ 25,252
% of 30 days past due to total retained loans	1.57%	1.75%
Home equity line of credit, open-ended revolving period	10 years
Home equity line of credit, amortization period	20 years
Consumer, excluding credit card | HELOCs, Beyond the revolving period | HELOCs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 10,509	$ 7,979
% of 30 days past due to total retained loans	3.03%	3.16%