Stock-based compensation - Stock options additional information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
2018 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised	$ 0.9	$ 3.8	$ 76.6
2020 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised	$ 0.5	$ 0.5	$ 1.9
Weighted average grant date fair value	$ 5.87	$ 6.93	$ 8.61