Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued compensation and related costs	$ 5,546	$ 7,098
Accrued professional services	3,454	2,511
Accrued insurance premiums	675	476
Other accrued expenses	1,006	1,133
Total accrued liabilities	$ 10,681	$ 11,218