Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Development and clinical manufacturing costs	$ 7,046	$ 3,910
Payroll and payroll-related costs	5,020	4,962
Facility and other	3,141	3,641
Total accrued expenses and other current liabilities	$ 15,207	$ 12,513