Loans - Net Gains and Losses on Sale (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Loans and Leases Receivable Disclosure [Line Items]
Total net gains/(losses) on sales of loans (including lower of cost or fair value adjustments)	$ 101	$ 66
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Total net gains/(losses) on sales of loans (including lower of cost or fair value adjustments)	91	42
Credit card
Loans and Leases Receivable Disclosure [Line Items]
Total net gains/(losses) on sales of loans (including lower of cost or fair value adjustments)	16	0
Wholesale
Loans and Leases Receivable Disclosure [Line Items]
Total net gains/(losses) on sales of loans (including lower of cost or fair value adjustments)	$ (6)	$ 24