Customer Deposits (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
U.S.:
Interest-bearing	$ 53,123	$ 52,316
Non-interest-bearing	322	367
Non-U.S.:
Interest-bearing	34	58
Non-interest-bearing	311	301
Total customer deposits	53,790	53,042
Card Member Credit Balances [Member]
U.S.:
Non-interest-bearing	286	331
Non-U.S.:
Non-interest-bearing	$ 299	$ 285