Stock-Based Compensation and Stock Options and Awards - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Costs and expenses:
Total stock-based compensation expense	$ 386	$ 256	$ 1,185	$ 698
Research and Development [Member]
Costs and expenses:
Total stock-based compensation expense	190	150	564	367
General and Administrative [Member]
Costs and expenses:
Total stock-based compensation expense	$ 196	$ 106	$ 621	$ 331