Accrued Expenses - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts Payable and Accrued Liabilities [Line Items]
Accrued expenses	$ 506	$ 739
Accrued Vacation And Bonus	300	100
Accrued Preclinical Expenses	100
Accrued Clinical And Preclinical		400
Accrued License Maintenance Fee	$ 100	100
Other Accrued Liabilities		$ 100