Customer Deposits (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
U.S.:
Interest-bearing	$ 54,102	$ 43,279
Non-interest-bearing	478	418
Non-U.S.:
Interest-bearing	82	115
Non-interest-bearing	335	359
Total customer deposits	54,997	44,171
Card Member Credit Balances [Member]
U.S.:
Non-interest-bearing	389	372
Non-U.S.:
Non-interest-bearing	$ 323	$ 347