Property and Equipment - Summary of Major Classes of Property and Equipment (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 923	$ 769
Less accumulated depreciation	(483)	(363)
Property and equipment, net	440	406
Land, buildings and leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	324	333
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	446	338
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	81	72
Transportation equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 72	$ 26