Share-based compensation - Activity (Details)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Aug. 31, 2020 USD ($) employee shares	Jun. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2020 USD ($) $ / shares	Dec. 31, 2020 $ / shares shares	Sep. 30, 2020 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Share-based Payment Arrangement, Expense | $	$ 0	$ 749,000	$ 39,000	$ 1,074,000	$ 185,000
Fair value of option price per share							$ 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				1,472,840
Options, Granted | shares				581,231
Options, Forfeited | shares				(5,505)
Options, Exercised | shares				(32,530)
Options, Ending balance | shares		2,016,036		2,016,036		1,472,840
Options, Exercisable | shares		705,784		705,784
Options, Vested and expected to vest | shares		2,016,036		2,016,036
Weighted Average Exercise price
Beginning price				$ 3.14
Granted				25.60
Forfeited				8.10
Exercised				0.82
Ending price		$ 9.64		9.64		$ 3.14
Exercisable		1.13		1.13
Vested and expected to vest		$ 9.64		$ 9.64
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contractual Term				8 years 6 months 14 days		8 years 6 months 3 days
Weighted Average Remaining Contractual Term, Exercisable				7 years 1 month 20 days
Weighted Average Remaining Contractual Term, Vested and expected to vest				8 years 6 months 14 days
Weighted average grant date fair value				$ 18.00	$ 1.32
Intrinsic value, exercised | $				$ 800,000
Intrinsic value, outstanding | $		$ 20,300,000		$ 20,300,000