Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accrued Expenses And Other Current Liabilities [Abstract]
Salary and related expenses	$ 7,260	$ 3,814
Current portion of milestone rights liability	1,643
Professional fees	1,007	875
Discounts and allowances for commercial product sales	873	754
Sales and marketing services	147	144
Restructuring	362	1,376	$ 3,028
Accrued interest	567	619
Other	590	355
Accrued expenses and other current liabilities	$ 12,449	$ 7,937