Collaboration Agreements - AskBio (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Operating expenses	$ 16,367	$ 16,248	$ 35,189	$ 28,114
AskBio License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Operating expenses	$ 800		$ 2,000
Cost share percentage			50.00%