Loans - Net Gains and Losses on Sale (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total net gains/(losses) on sales of loans (including lower of cost or fair value adjustments)	$ 108	$ 114	$ 293	$ 267
Consumer, excluding credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total net gains/(losses) on sales of loans (including lower of cost or fair value adjustments)	62	97	239	223
Credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total net gains/(losses) on sales of loans (including lower of cost or fair value adjustments)	13	(9)	22	(9)
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total net gains/(losses) on sales of loans (including lower of cost or fair value adjustments)	$ 33	$ 26	$ 32	$ 53