Accrued Expenses and Other - Schedule of Accrued Expenses and Other (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Payroll	$ 1,795	$ 1,643
Professional fees	2,006	1,074
Clinical studies	204	740
Other	1,361	1,814
Restructuring	249
Total	$ 5,615	$ 5,271