Net loss per share - Antidilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potentially dilutive securities (in shares)	20,933,142	7,895,468
Stock options outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potentially dilutive securities (in shares)	5,119,730	6,521,067
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potentially dilutive securities (in shares)	8,219,810	1,374,401
Shares related to the 2026 Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potentially dilutive securities (in shares)	7,475,897	0
Shares committed under the 2021 ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potentially dilutive securities (in shares)	117,705	0