Loans - Net Gains and Losses on Sale (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Loans and Leases Receivable Disclosure [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	$ 340	$ 201	$ 240
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	305	341	313
Credit card
Loans and Leases Receivable Disclosure [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	1	(241)	3
Wholesale
Loans and Leases Receivable Disclosure [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	$ 34	$ 101	$ (76)