Guarantees (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Type of Guarantee
Maximum potential amount of undiscounted future payments	$ 51,000	$ 48,000
Amount of related liability	86	86
Return And Merchant Protection [Member]
Type of Guarantee
Maximum potential amount of undiscounted future payments	45,000	42,000
Amount of related liability	37	37
Other Guarantees [Member]
Type of Guarantee
Maximum potential amount of undiscounted future payments	6,000	6,000
Amount of related liability	$ 49	$ 49