Summary of significant accounting policies - Anti-dilutive (Details) - shares	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Anti-dilutive securities	3,250,769	8,021,647
Stock options
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Anti-dilutive securities	1,936,546	1,316,267
Common stock warrants
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Anti-dilutive securities	1,314,223	1,035,196
Series A Preferred Convertible Stock
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Anti-dilutive securities		5,670,184

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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration