Accrued Expenses and Other Current Liabilities - Summary of Accrued Expense and Other Current Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Accrued expenses and other liabilities:
Accrued compensation and benefits	$ 4,246	$ 7,886
Accrued consulting and professional fees	2,788	3,841
Accrued research and development	1,361	1,855
Accrued other	10,675	5,357
Total accrued expenses and other current liabilities	19,070	$ 18,939
Accrued property, plant and equipment purchases	$ 5,800