Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended			3 Months Ended
	Aug. 31, 2018 USD ($)	Oct. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2019 USD ($) Payments	Jan. 31, 2017 USD ($)
Carna License Agreement [Member]
Loss Contingencies [Line Items]
Aggregate milestone payment				$ 270.0
Upfront payment paid			$ 0.9
Number of milestone payments recorded | Payments				0
Milestone payment				$ 4.0
CPF License Agreements [Member]
Loss Contingencies [Line Items]
Milestone payment					$ 2.0
Upfront payment paid		$ 7.0
Additional milestone payment payable				319.5
Asset Purchase Agreement [Member]
Loss Contingencies [Line Items]
Upfront payment paid	$ 3.0
Aggregate milestone payment				195.0
Milestone payment				$ 5.0