Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in the Card Member receivable reserve for losses
Balance, January 1	$ 145	$ 110	$ 114
Provisions	243	238	145
Other credits	53	58	20
Net write-offs	(238)	(198)	(146)
Other debits	(36)	(63)	(23)
Balance, December 31	$ 167	$ 145	$ 110