Guarantees (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Type of Guarantee
Maximum potential amount of undiscounted future payments	$ 49,000	$ 48,000
Amount of related liability	82	86
Return And Merchant Protection [Member]
Type of Guarantee
Maximum potential amount of undiscounted future payments	43,000	42,000
Amount of related liability	42	49
Other Guarantees [Member]
Type of Guarantee
Maximum potential amount of undiscounted future payments	6,000	6,000
Amount of related liability	$ 40	$ 37