Loans - Net Gains and Losses on Sale (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	$ 51	$ 101
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	53	91
Credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	0	16
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	$ (2)	$ (6)