Future Minimum Payments Under Loans Payable (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
2017	$ 4,386
2018	7,506
2019	7,159
Long-term Debt, Gross, Total	19,051
Less amount representing interest	(3,361)
Less unamortized discount	(997)	$ (500)
Less deferred charges	(690)
Less loans payable current, net of discount	(2,124)	(2,053)
Loans payable, net of current portion and discount	$ 11,879	$ 7,418