Reserves for Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Changes in the Card Member loans reserve for losses [Line Items]
Balance, January 1	$ 2,134	$ 1,706
Card Member loans provisions	525	499
Ending Balance	2,121	1,786
Other	11	10
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 and Fees	(457)	(358)
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 and Fees	$ (92)	$ (71)