Loans - Consumer, Excluding Credit Card Loan Portfolio, Other Consumer Impaired Loans and Loan Modifications (Details) - Consumer, excluding credit card - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 9,331	$ 12,493	$ 10,367	$ 12,806
Other Consumer
Financing Receivable, Impaired [Line Items]
With an allowance	512		512		$ 557
Without an allowance	32		32		35
Total impaired loans	544		544		592
Allowance for loan losses related to impaired loans	112		112		117
Unpaid principal balance of impaired loans	657		657		719
Impaired loans on nonaccrual status	430		430		456
Average impaired loans	543	$ 603	565	$ 701
Troubled debt restructuring	398		398		442
Impaired loans on nonaccrual status	$ 284		$ 284		$ 306