Guarantees (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Type of Guarantee
Maximum potential amount of undiscounted future payments	$ 50,000	$ 48,000
Amount of related liability	85	86
Return And Merchant Protection [Member]
Type of Guarantee
Maximum potential amount of undiscounted future payments	44,000	42,000
Amount of related liability	41	49
Other Guarantees [Member]
Type of Guarantee
Maximum potential amount of undiscounted future payments	6,000	6,000
Amount of related liability	$ 44	$ 37