Loans and Accounts Receivable (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Loans segment information
Card Member loans, gross	$ 72,820	$ 73,399
Less: Reserve for losses	1,786	1,706	$ 1,248	$ 1,223
Card Member loans, net	71,034	71,693
Other loans, less reserves	2,872	2,607
Accounts Receivable and Loans Textuals [Abstract]
Other loans, reserves	91	80
Variable Interest Enterprise [Member]
Loans segment information
Card Member loans, gross	24,058	25,695
U S Consumer Services [Member]
Loans segment information
Card Member loans, gross	52,655	53,668
U S Consumer Services [Member] | Variable Interest Enterprise [Member]
Accounts Receivable and Loans Textuals [Abstract]
Gross Card Member loans available to settle the obligations of a variable interest entity	24,100	25,700
International Consumer and Network Services [Member]
Loans segment information
Card Member loans, gross	8,667	8,651
Global Commercial Services [Member]
Loans segment information
Card Member loans, gross	$ 11,498	$ 11,080