Customer Deposits (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
U.S.:
Interest-bearing	$ 54,934	$ 54,102
Non-interest-bearing	405	478
Non-U.S.:
Interest-bearing	87	82
Non-interest-bearing	338	335
Total customer deposits	55,764	54,997
Card Member Credit Balances [Member]
U.S.:
Non-interest-bearing	372	389
Non-U.S.:
Non-interest-bearing	$ 317	$ 323