Leases - Summary of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Finance lease cost	$ 21	$ 23	$ 21		$ 21
Interest expense	1	3	4		4
Operating lease cost			5,565	$ 310	128
Research and development
Lessee, Lease, Description [Line Items]
Finance lease cost	$ 20	$ 20	17		17
Operating lease cost			4,272	0	0
General and administrative expenses
Lessee, Lease, Description [Line Items]
Operating lease cost			$ 1,293	$ 310	$ 128