Customer Deposits (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
U.S.:
Interest-bearing	$ 41,947	$ 39,649
Non-interest-bearing	178	10
Non-U.S.:
Interest-bearing	125	135
Non-interest-bearing	237	9
Total customer deposits	42,487	39,803
Card Member Credit Balances [Member]
U.S.:
Non-interest-bearing	160	0
Non-U.S.:
Non-interest-bearing	$ 228	$ 0