Reserves for Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in the Card Member loans reserve for losses [Line Items]
Balance, January 1	$ 1,706	$ 1,223	$ 1,028
Card Member loans provisions	2,266	1,868	1,235
Balance, December 31	2,134	1,706	1,223
Provisions for loans and lease losses deductions net write offs principal
Changes in the Card Member loans reserve for losses [Line Items]
Net Write-Offs Principal, Interest, Fees and Other	(1,539)	(1,181)	(930)
Provisions for loans and lease losses deductions net write offs interest and fees
Changes in the Card Member loans reserve for losses [Line Items]
Net Write-Offs Principal, Interest, Fees and Other	(304)	(227)	(175)
Provisions for loans and lease losses other
Changes in the Card Member loans reserve for losses [Line Items]
Net Write-Offs Principal, Interest, Fees and Other	$ 5	$ 23	$ 65