Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accrued expenses and other liabilities:
Accrued compensation and benefits	$ 6,822	$ 10,438
Accrued consulting and professional fees	4,130	3,927
Accrued research and development	6,692	7,503
Accrued revenue reserves	16,500	10,155
Accrued other	1,666	6,358
Total accrued expenses and other current liabilities	$ 35,810	$ 38,381