Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in the Card Member receivable reserve for losses
Balance, January 1	$ 114	$ 94	$ 76
Provisions	145	160	194
Other credits	20	32	15
Net write-offs	(146)	(157)	(166)
Other debits	(23)	(15)	(25)
Balance, December 31	$ 110	$ 114	$ 94