Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Development and clinical manufacturing costs	$ 3,350	$ 1,436
Payroll and payroll-related costs	3,698	2,756
Professional fees	448	184
Facility and other	3,316	1,147
Total Accrued Expenses and Other Current Liabilities	$ 10,812	$ 5,523