Customer Deposits (Details 1) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
U.S. retail deposits:
Savings accounts - Direct	$ 35,336	$ 31,915
Certificates of deposit - Direct	374	290
Certificates of deposit - Third party	16,308	16,684
Sweep accounts - Third party	14,618	14,777
Other retail deposits:
U.S. non-interest bearing deposits, Other	35	37
Non-US Deposits, Other	47	47
Card Member credit balances - U.S. and non-U.S.	673	702
Total customer deposits	$ 67,391	$ 64,452