Customer Deposits (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
U.S.:
Interest-bearing	$ 53,666	$ 54,102
Non-interest-bearing	343	478
Non-U.S.:
Interest-bearing	89	82
Non-interest-bearing	306	335
Total customer deposits	54,404	54,997
Card Member Credit Balances [Member]
U.S.:
Non-interest-bearing	311	389
Non-U.S.:
Non-interest-bearing	$ 293	$ 323