Summary of significant accounting policies - Anti-dilutive (Details) - shares	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Anti-dilutive securities	8,021,647	3,701,705
Stock options
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Anti-dilutive securities	1,316,267	592,929
Convertible preferred stock warrants
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Anti-dilutive securities	1,035,196
Series A Preferred Stock
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Anti-dilutive securities	5,670,184	3,108,776

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