Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Depreciation and amortization	$ 51,848	$ 35,193	$ 28,034
Accelerated depreciation and amortization expense			1,900
Capitalized developed software costs	26,000	15,600	8,000
Property And Equipment Excluding Developed Software
Property Plant And Equipment [Line Items]
Depreciation and amortization	11,700	8,900	5,700
Developed software
Property Plant And Equipment [Line Items]
Depreciation and amortization	$ 12,000	$ 5,400	$ 4,100