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		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Financing Receivable, Impaired [Line Items]
Average impaired loans	$ 8,975	$ 11,269
Other Consumer
Financing Receivable, Impaired [Line Items]
With an allowance	545		$ 527
Without an allowance	31		31
Total impaired loans	576		558
Allowance for loan losses related to impaired loans	114		118
Unpaid principal balance of impaired loans	685		668
Impaired loans on nonaccrual status	445		449
Average impaired loans	571		587
Troubled debt restructuring	369		384
Impaired loans on nonaccrual status	$ 238		$ 275