License and Acquisition Agreements - Primatope Stock Purchase Option Agreement (Details) $ in Thousands	1 Months Ended		3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($)	Sep. 30, 2017 USD ($) item	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2019 USD ($)
License and Acquisition Agreements
Research and development			$ 20,901	$ 59,253
Primatope | Stock Option Purchase Agreement
License and Acquisition Agreements
Percentage of capital stock available to purchase in call option		100.00%
Payment for extension of option period					$ 800
Primatope Acquisition
License and Acquisition Agreements
Purchase price	$ 18,000
Upfront consideration payable on exercise of call option to acquire all outstanding equity	10,000			10,000
Milestone payment payable after achievement of specified milestones	$ 5,000			5,000		$ 3,000
Research and development				$ 18,000
Primatope Acquisition | Stock Option Purchase Agreement
License and Acquisition Agreements
Upfront payment for initial option period		$ 500
Maximum | Primatope | Stock Option Purchase Agreement
License and Acquisition Agreements
Number of extensions allowed for initial option period | item		3
Total aggregate extension payments		$ 800