Share-based compensation - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Jun. 11, 2020	Jun. 07, 2018	Sep. 17, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share based compensation expense	$ 0.6	$ 0.4
Common stock reserved for issuance	4,776,228
Options granted	354,838	415,478
Stock option vesting period	2 years
Share-based compensation arrangement by share based payment award percentage of fair market Person holding more then 10% voting stock	110.00%
Intrinsic value of options outstanding	$ 16.0		$ 8.9
Intrinsic value of options unvested	0.6		$ 0.0
Intrinsic value of options exercised	$ 1.8	$ 1.6
Employee Stock Option
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Option to purchase granted			463,754
Options vested			20,500
Minimum
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Options outstanding	3 years
Maximum
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Options outstanding	10 years
2014 Stock Incentive Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Common stock reserved for issuance						3,000,000
2018 Stock Incentive Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Common stock reserved for issuance					4,000,000
2020 Stock Incentive Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Common stock reserved for issuance				3,000,000
Stock Option Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Options granted	354,838		484,254