Customer Deposits (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
U.S.:
Interest-bearing	$ 41,853	$ 40,831
Non-interest-bearing	317	360
Non-U.S.:
Interest-bearing	110	121
Non-interest-bearing	391	451
Total customer deposits	42,671	41,763
Card Member Credit Balances [Member]
U.S.:
Non-interest-bearing	298	340
Non-U.S.:
Non-interest-bearing	$ 373	$ 437