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Composition of Balance Sheet Items - Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Property and equipment
Finance lease assets (1)	$ 0		$ 0		$ 22,747
Total property and equipment, gross	27,624		27,624		54,864
Less accumulated depreciation and amortization	(10,559)		(10,559)		(17,040)
Property and equipment, net	17,065		17,065		37,824
Depreciation and amortization expense	700	$ 600	1,300	$ 1,100
Lab equipment and furniture
Property and equipment
Property and equipment, gross	11,992		11,992		12,526
Leasehold improvements
Property and equipment
Property and equipment, gross	12,453		12,453		15,183
Software
Property and equipment
Property and equipment, gross	2,023		2,023		2,295
Computer equipment
Property and equipment
Property and equipment, gross	$ 1,156		$ 1,156		$ 2,113