Loan and Security Agreement - Future Minimum Payments under the Loan and Security Agreement (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Amount due in 2017	$ 4,914
Amount due in 2018	13,675
Amount due in 2019	22,548
Amount due in 2020	25,411
Total future minimum payments	66,548
Unamortized interest	(16,445)
Debt discount	(1,377)
Capitalized debt issuance costs	(1,619)
Total minimum payment	47,107
Current portion	(209)	$ (4,835)
Long-term debt	$ 47,107	$ 4,394