Research and License Agreements - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Jan. 31, 2017 USD ($) LicenseAgreement	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
License Agreements
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research agreement date		2013-12
Number of license agreements | LicenseAgreement	2
Maximum future contingent license payment	$ 6,400,000
Aggregate potential milestone payments for receipt of regulatory approval	5,000,000
Aggregate potential milestone payments for final regulatory approval of second indication	$ 500,000
Annual license fees paid		$ 50,000	$ 30,000	$ 10,000
License Agreements | Minimum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Rate of revenue share	6.50%
License Agreements | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Rate of revenue share	25.00%
University Research Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Payments pursuant to research agreements		$ 200,000	$ 600,000	$ 800,000