Accrued Expenses - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Payroll and employee-related costs	$ 14,140	$ 13,044
Professional services	3,966	2,221
Property and equipment purchases	423	115
Other	6,740	5,198
Accrued expenses	$ 25,269	$ 20,578