Accrued Expenses - Components of Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Development costs	$ 1,156	$ 931
Employee compensation	855	573
Professional fees	355	194
Interest	0	88
Other	126	8
Total accrued expenses	$ 2,492	$ 1,794