Customer Deposits (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
U.S.:
Interest-bearing	$ 52,767	$ 54,102
Non-interest-bearing	333	478
Non-U.S.:
Interest-bearing	88	82
Non-interest-bearing	312	335
Total customer deposits	53,500	54,997
Card Member Credit Balances [Member]
U.S.:
Non-interest-bearing	297	389
Non-U.S.:
Non-interest-bearing	$ 297	$ 323