Nature of the Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands					1 Months Ended		3 Months Ended	12 Months Ended
	Feb. 25, 2020	Feb. 19, 2020	Sep. 03, 2019	Aug. 19, 2019	Aug. 31, 2020	Feb. 29, 2020	Sep. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Nature Of Business And Basis Of Presentation [Line Items]
Issuance of common stock sold, net of underwriting discounts, commissions, and offering costs								$ 8,549	$ 206,276	$ 431,780
Net loss								(299,964)	(266,489)	$ (192,256)
Accumulated deficit								(1,054,432)	$ (754,468)
Cash, cash equivalents and marketable securities								$ 327,600
Common Shares
Nature Of Business And Basis Of Presentation [Line Items]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)								172,094	3,953,365	12,432,431
Issuance of common stock sold, net of underwriting discounts, commissions, and offering costs								$ 2	$ 40	$ 124
Follow On Offering | Common Shares
Nature Of Business And Basis Of Presentation [Line Items]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)	477,272	3,181,818	1,621,621	10,810,810		3,659,090	12,432,431
Additional offering price of common stock (in dollars per share)	$ 55.00	$ 55.00	$ 37.00	$ 37.00		$ 55.00	$ 37.00
Issuance of common stock sold, net of underwriting discounts, commissions, and offering costs	$ 24,700	$ 163,700	$ 56,400	$ 375,400		$ 188,400	$ 431,800
Open Market Sale Agreement
Nature Of Business And Basis Of Presentation [Line Items]
Authorized aggregate offering proceeds					$ 200,000
Available for future issuance								$ 172,500
Open Market Sale Agreement | Common Shares
Nature Of Business And Basis Of Presentation [Line Items]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)								172,094	294,275
Issuance of common stock sold, net of underwriting discounts, commissions, and offering costs								$ 8,500	$ 17,900