Reduction in Workforce - Narrative (Details) $ in Thousands		1 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Jul. 31, 2021 employee	Apr. 30, 2021 USD ($) employee	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring expense				$ 20,175	$ 0	$ 24,800	$ 0
Stock-based compensation expense				28,338	$ 38,818	101,863	$ 123,640
April 2021 reduction
Restructuring Cost and Reserve [Line Items]
Number of employees impacted | employee			50
Restructuring expense			$ 4,600			4,625
July 2021 reduction
Restructuring Cost and Reserve [Line Items]
Number of employees impacted | employee		90
Restructuring expense				$ 20,200		$ 20,175
July 2021 reduction | Unrestricted Stock Awards
Restructuring Cost and Reserve [Line Items]
Stock-based compensation expense	$ 2,500