Customer Deposits (Details 1) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
U.S. retail deposits:
Savings accounts - Direct	$ 30,780	$ 30,980
Certificates of deposit - Direct	290	291
Certificates of deposit - Third party	17,229	11,925
Sweep accounts - Third party	12,274	9,120
Other retail deposits:
U.S. non-interest bearing deposits, Other	37	36
Non-US Deposits, Other	46	74
Card Member credit balances - U.S. and non-U.S.	634	616
Total customer deposits	$ 61,290	$ 53,042