Net income (loss) per share - Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss per Share Attributable to Common Stockholders (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	5,377	6,775	5,377	1,440
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	1,604	2,282	1,604	658
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	3,274	3,622	3,274	80
Market-based restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	134	612	134	612
Performance-based restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	240	90	240	90
Employee stock purchase plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share
Potentially dilutive securities, excluded from computation of diluted net income (loss) per share (in shares)	125	169	125	0