License Agreements - AstraZeneca (Details) - USD ($)	1 Months Ended			3 Months Ended
	Aug. 31, 2019	Sep. 30, 2018	Jul. 31, 2018	Mar. 31, 2020	Mar. 31, 2019
AstraZeneca
Research and Development Arrangement, Contract to Perform for Others [Line Items]
License agreement, cash payment	$ 2,000,000.0		$ 1,000,000.0	$ 0	$ 0
Maximum milestone payments for licensed products				12,500,000
Maximum milestone payments for net worldwide sales				$ 15,000,000.0
Series B
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Preferred stock issued (in shares)		9,364,850
Series B | AstraZeneca
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Preferred stock issued (in shares)			484,388
Preferred stock issued			$ 3,000,000.0