Reserves (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Changes in the Card Member receivable reserve for losses
Balance, January 1	$ 110	$ 114
Provisions	113	64
Other credits	33	6
Net write-offs	(94)	(75)
Other debits	(16)	(10)
Balance, June 30	$ 146	$ 99