Basis of Presentation and Summary of Significant Accounting Policies - Accounting for Share-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Basis of Presentation [Line Items]
Share-based compensation expense	$ 9,754	$ 7,740	$ 28,375	$ 20,752
SBC - Research and development expenses
Basis of Presentation [Line Items]
Share-based compensation expense	4,480	3,094	12,975	8,510
SBC - General and administrative expenses
Basis of Presentation [Line Items]
Share-based compensation expense	$ 5,274	$ 4,646	$ 15,400	$ 12,242