Loans - Consumer, Excluding Credit Card Loan Portfolio, Delinquency Statistics Junior Lien Home Equity Loans (Details) - USD ($) $ in Millions	3 Months Ended
	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
Total 30 plus day delinquency rate	2.66%	2.77%
Consumer, excluding credit card | Home equity | Junior lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 29,388	$ 30,711
Total 30 plus day delinquency rate	2.10%	2.25%
Consumer, excluding credit card | HELOANs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 2,266	$ 2,409
Total 30 plus day delinquency rate	2.87%	3.03%
Consumer, excluding credit card | HELOCs, Within the revolving period | HELOCs
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 15,136	$ 17,050
Total 30 plus day delinquency rate	1.38%	1.57%
Open-ended revolving period	10 years
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	$ 11,986	$ 11,252
Total 30 plus day delinquency rate	2.85%	3.10%