Debt - Principal Payments on Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
2018	$ 4,109
2019	3,423
2020	13,675
2021	21,667
Total	42,874
Add: capital lease principal payments	222	$ 480
Less: debt discount	(2,023)	(3,543)
Total	41,073	46,205
Less: current portion of long-term debt	(3,306)	(3,113)
Long-term debt, net of current portion	$ 37,767	$ 43,092