Share-based compensation - Activity (Details)	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares	Aug. 31, 2020 USD ($) employee shares	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) $ / shares	Dec. 31, 2019 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Stock-based compensation expense | $	$ 800,000	$ 0	$ 117,000	$ 1,000	$ 302,000	$ 11,000
Fair value of option price per share	$ 8.69		$ 8.69		$ 8.69
Two Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Granted | shares		92,169
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number Of Employees Granted Stock Options | employee		2
The Plans
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options, Beginning balance | shares					583,622
Options, Granted | shares					760,698
Forfeited | shares					(2,707)
Options, Exercised | shares					(25,346)
Options, Ending balance | shares	1,316,267		1,316,267		1,316,267		583,622
Options, Exercisable | shares	468,172		468,172		468,172
Options, Vested and expected to vest | shares	1,316,267		1,316,267		1,316,267
Weighted Average Exercise price
Beginning price					$ 0.47
Granted					1.33
Forfeited					0.50
Exercised					0.47
Ending price	$ 0.97		$ 0.97		0.97		$ 0.47
Exercisable	0.75		0.75		0.75
Vested and expected to vest	$ 0.97		$ 0.97		$ 0.97
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contractual Term					7 years 7 months 13 days		6 years 3 months 18 days
Weighted Average Remaining Contractual Term, Exercisable					6 years 4 months 24 days
Weighted Average Remaining Contractual Term, Vested and expected to vest					7 years 7 months 13 days
Weighted average grant date fair value					$ 0.87	$ 0.24
Intrinsic value, exercised | $					$ 300,000
Intrinsic value, outstanding | $	$ 14,500,000		$ 14,500,000		$ 14,500,000