Customer Deposits (Details 1) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
U.S. retail deposits:
Savings accounts - Direct	$ 37,128	$ 31,915
Certificates of deposit - Direct	610	290
Certificates of deposit - Third party	15,219	16,684
Sweep accounts - Third party	15,615	14,777
Other retail deposits:
U.S. non-interest bearing deposits, Other	34	37
Non-US Deposits, Other	38	47
Card Member credit balances - U.S. and non-U.S.	657	702
Total customer deposits	$ 69,301	$ 64,452