Stock-based compensation - Stock Options - Narrative (Details) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2021 USD ($) shares	Sep. 30, 2021 USD ($) $ / shares shares
2020 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares) | shares		546
Total outstanding shares (in shares)	$ 2.0	$ 2.0
Options outstanding, intrinsic value	37.0	37.0
Unrecognized compensation expense, options	$ 6.9	$ 6.9
Period for recognition		2 years 11 months 19 days
Non-Statutory Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield		0.00%
Grant date fair value of common stock (in dollars per share) | $ / shares		$ 18.60
Non-Statutory Stock Options | 2020 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares) | shares	320	550
Exercise term	10 years
Options vested and outstanding (in shares) | shares		490
Options granted, fair value		$ 4.0
Grant date fair value of common stock (in dollars per share) | $ / shares		$ 7.35
Non-Statutory Stock Options | 2020 Equity Incentive Plan | One year after the grant date
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%
Non-Statutory Stock Options | 2020 Equity Incentive Plan | Subsequent three-month anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		6.25%