Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Development and manufacturing costs	$ 6,494	$ 3,910
Payroll and payroll-related costs	2,033	4,962
Professional fees	330	344
Facility and other	3,016	3,297
Total Accrued Expenses and Other Current Liabilities	$ 11,873	$ 12,513