Stock-based compensation - Narrative (Details) $ in Millions		1 Months Ended	3 Months Ended
	Oct. 12, 2020 USD ($) shares	Mar. 31, 2021 USD ($)	Mar. 31, 2022 USD ($) plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Number of equity incentive plans | plan			3
Unamortized stock-based compensation expense of option			$ 21.2
Management And Employee | 2015 Stock Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Vested Options, exercised in period (in shares) | shares	2,883,672
Unvested Options, exercised in period (in shares) | shares	4,603,833
Certain Executives
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Proceeds from noteholders debt		$ 0.3
Certain Executives | 2015 Stock Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation cost upon forgiveness of promissory notes			$ 0.3
Convertible Promissory Note | Notes Payable, Other Payables | Management And Employee
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Convertible notes, outstanding balance	$ 1.1
Debt instrument, stated interest rate	0.38%
Stock options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Unamortized stock-based compensation expense, period for recognition			2 years 4 months 24 days
Restricted Stock Units
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based payment arrangement, cost not yet recognized, RSU			$ 68.1
Award vesting period			3 years 2 months 12 days