Summary of Significant Accounting Policies - Revenue Recognition - Collaboration Revenue (Details) - USD ($)		3 Months Ended		6 Months Ended
	Sep. 24, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Collaboration Revenue
Collaboration revenue		$ 0	$ 0	$ 0	$ 0
Knight
Collaboration Revenue
License agreement term (in years)	15 years
Transfer price receivable upon achievement of certain regulatory and sales milestones	$ 18,000,000