Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Payroll and employee-related costs	$ 7,870	$ 5,011
Professional services	2,185	1,123
Property and equipment purchases	4,410	471
Other	1,604	809
Accrued expenses	$ 16,069	$ 7,414