Customer Deposits (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
U.S.:
Interest-bearing	$ 41,883	$ 40,831
Non-interest-bearing	336	360
Non-U.S.:
Interest-bearing	108	121
Non-interest-bearing	376	451
Total customer deposits	42,703	41,763
Card Member Credit Balances [Member]
U.S.:
Non-interest-bearing	304	340
Non-U.S.:
Non-interest-bearing	$ 361	$ 437