Commitments and Contingencies - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) ft²	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) ft²	Jun. 30, 2018 USD ($)	Jan. 01, 2019 USD ($)
Operating Leased Assets [Line Items]
Right-of-use asset	$ 2,906		$ 2,906
Rent expense	$ 174	$ 34	$ 299	$ 65
2016 Lease Agreement [Member]
Operating Leased Assets [Line Items]
Lease expiration date			Feb. 28, 2027
Additional area of real estate property leased | ft²	31,000		31,000
Clinical Supply Agreement [Member]
Operating Leased Assets [Line Items]
Estimated remaining commitment	$ 2,500		$ 2,500
Project management service fee	$ 1,100	$ 662	$ 1,900	$ 1,500
ASU 2016-02 [Member]
Operating Leased Assets [Line Items]
Right-of-use asset					$ 3,100
Operating lease, liability					$ 3,400