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Property and Equipment, Net - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Property Plant And Equipment [Abstract]        
Depreciation and amortization $ 2.6 $ 1.6 $ 6.7 $ 4.1