Loans - Consumer, Excluding Credit Card Loans, Delinquency Statistics Junior Lien Home Equity Loans (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 779,705	$ 747,508	$ 735,369
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	316,781	294,979	$ 288,214
Consumer, excluding credit card | Home equity - junior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 33,434	$ 36,375
% of 30 days past due to total retained loans	2.06%	2.20%
Consumer, excluding credit card | Home equity junior lien, excluding lines of credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 2,774	$ 3,144
% of 30 days past due to total retained loans	2.70%	3.34%
Consumer, excluding credit card | HELOC, Within the revolving period | Home equity line of credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 21,023	$ 25,252
% of 30 days past due to total retained loans	1.61%	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 | Home equity line of credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 9,637	$ 7,979
% of 30 days past due to total retained loans	2.84%	3.16%