Customer Deposits (Details 1) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
U.S. retail deposits:
Savings accounts - Direct	$ 31,915	$ 30,980
Certificates of deposit - Direct	290	291
Certificates of deposit - Third Party	16,684	11,925
Sweep accounts - Third party	14,777	9,120
Other Customer Deposits
U.S. non-interest bearing deposits	37	36
Non-US deposits	47	74
Card Member credit balances - U.S. and non-U.S.	702	616
Total customer deposits	$ 64,452	$ 53,042