Accrued Expense - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts Payable and Accrued Liabilities [Line Items]
Accrued expense	$ 304	$ 739
Accrued Vacation And Bonus	100	100
Accrued Clinical And Preclinical Expenses	100	400
Accrued License Maintenance Fee		100
Other Accrued Liabilities		$ 100
Accrued Legal And Professional Fee	$ 100