Property Plant and Equipment - Components of Property Plant and Equipment (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 154,578	$ 156,096
Accumulated depreciation and amortization	(92,978)	(82,695)
Property, plant and equipment, net	61,600	73,401
Vehicles
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 44,620	45,050
Vehicles | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	3 years
Vehicles | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 58,489	53,891
Computer equipment and software | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	3 years
Computer equipment and software | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 27,977	26,401
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	2 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	15 years
Office furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 20,416	19,532
Estimated Useful Lives	7 years
Build-to-suit lease building
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 0	8,247
Estimated Useful Lives	10 years 6 months
Construction in process
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 3,076	$ 2,975