Reserves (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Changes in the Card Member receivable reserve for losses
Balance, January 1	$ 110	$ 114
Provisions	60	34
Other credits	10	6
Net write-offs	(47)	(36)
Other debits	(5)	0
Balance, March 31	$ 128	$ 118