Loans - Net Gains and Losses on Sale (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans and Leases Receivable Disclosure [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	$ 245	$ 340	$ 201
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)	231	305	341
Credit card
Loans and Leases Receivable Disclosure [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	(12)	1	(241)
Wholesale
Loans and Leases Receivable Disclosure [Line Items]
Total net gains on sales of loans (including lower of cost or fair value adjustments)	$ 26	$ 34	$ 101