Quarterly Financial Data (unaudited) - Summary of Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Revenue	$ 2,142		$ 1,746		$ 1,541		$ 1,358		$ 1,445		$ 650		$ 224		$ 0		$ 6,787	$ 2,319	$ 379
Operating expenses	18,435		13,212		11,909		7,508		7,492		5,856		4,129		2,174		51,064	19,651	10,877
Other income (expense)	18		27		(188)		65		(4,354)		(1,462)		(1,211)		(375)		(78)	(7,402)	(718)
Net loss	$ (16,275)		$ (11,439)		$ (10,556)		$ (6,085)		$ (10,401)		$ (6,668)		$ (5,116)		$ (2,549)		$ (44,355)	$ (24,734)	$ (11,216)
Net loss per share/unit, basic and diluted	$ (0.43)	[1]	$ (0.31)	[1]	$ (1.23)	[1]	$ (2.14)	[1]	$ (3.75)	[1]	$ (2.43)	[1]	$ (1.89)	[1]	$ (0.97)	[1]	$ (2.05)	$ (9.12)	$ (4.53)

[1] Net loss per share/unit is computed independently for each quarter and the full year based upon respective shares/units outstanding; therefore, the sum of the quarterly net loss per share/unit amounts may not equal the annual amounts reported.