Subsequent Event - Additional Information (Detail) - Collaboration and License Agreement - United Therapeutics Corporation - USD ($)	Nov. 04, 2019	Mar. 29, 2019	Sep. 30, 2019
Subsequent Event [Line Items]
Milestone Payment Received		$ 12,500,000
Maximum
Subsequent Event [Line Items]
Potential milestone payments to be receive			$ 37,500,000
Subsequent Event
Subsequent Event [Line Items]
Milestone Payment Received	$ 12,500,000
Subsequent Event | Maximum
Subsequent Event [Line Items]
Potential milestone payments to be receive	$ 25,000,000