Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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- Definition

The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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Net (loss) income per share - Potentially Anti-Dilutive Securities Excluded From Calculation of Diluted Net (Loss) Income per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net loss per share
Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	14,768,189	16,371,576	14,768,189	20,726,380
Stock options
Net loss per share
Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	12,947,009	11,613,978	12,947,009	12,912,267
Weighted-average number of shares of adjustments		86,000
Restricted stock units
Net loss per share
Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	1,749,979	807,566	1,749,979	3,758,548
Weighted-average number of shares of adjustments		137,000
2018 Notes
Net loss per share
Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	41,873	3,950,032	41,873	3,950,032
Employee Stock Purchase Plan
Net loss per share
Potentially anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	29,328		29,328	105,533
Weighted-average number of shares of adjustments		27,000