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Stock-based compensation - Narrative (Details) - USD ($) shares in Millions, $ in Millions				12 Months Ended
	Dec. 10, 2021	Feb. 12, 2021	Mar. 05, 2020	Dec. 31, 2021	Dec. 31, 2020	Feb. 10, 2021
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period for recognition				2 years 2 months 15 days
Unrecognized compensation expense, excluding options				$ 12.7
Performance stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period for recognition				1 month 28 days
Unrecognized compensation expense, excluding options				$ 0.3
Number of shares issued (in shares)	0.7	0.7
Shares withheld for tax obligations (in shares)	0.7	0.8
Tax withholding obligation	$ 25.4	$ 10.8
Performance factor percentage						250.00%
2018 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Accelerated cost			$ 2.5	$ 3.4	$ 2.5
Expiration term				10 years
Unrecognized compensation expense, option				$ 0.1
2018 Stock Plan \| Non-Statutory Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period for recognition				1 year 8 months 4 days
2020 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration term				10 years
Number of shares authorized (in shares)			16.3
Remaining shares available for issuance (in shares)				10.3
Unrecognized compensation expense, option				$ 8.7
2020 Equity Incentive Plan \| Non-Statutory Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period for recognition				2 years 10 months 20 days
2020 Equity Incentive Plan \| Non-Statutory Stock Options \| One year after the grant date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage				25.00%
2020 Equity Incentive Plan \| Non-Statutory Stock Options \| Subsequent three-month anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage				6.25%
2020 Equity Incentive Plan \| Performance stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum payout, percentage				300.00%
Vesting percentage, revenue growth				50.00%
Vesting percentage, contribution margin				50.00%