Accrued Expenses - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts Payable and Accrued Liabilities [Line Items]
Accrued expenses	$ 793	$ 739
Accrued Vacation And Bonus	200	100
Accrued Clinical And Preclinical	400	400
Accrued License Maintenance Fee	100	100
Other Accrued Liabilities	$ 100	$ 100