Operating Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Leases
Rent expense attributable to warehouse, office buildings and equipment operating leases	$ 72	$ 63	$ 57
Minimum future rentals under operating leases
2016	82
2017	78
2018	73
2019	65
2020	65
2021 and thereafter	$ 42