Stockholders’ deficit and stock-based compensation - Partial recourse promissory notes (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Class of Stock [Line Items]
Issuance of Common Stock upon exercise of options (in shares)	139,423	12,796,353
Class B Common Stock
Class of Stock [Line Items]
Issuance of Common Stock upon exercise of options (in shares)	365,605		365,605
Restricted Stock | Class A Common Stock
Class of Stock [Line Items]
Stock issued (in shares)	186,124		186,124
Partial Recourse Promissory Notes
Class of Stock [Line Items]
Due from employees	$ 0.2		$ 0.2
Percent of original principal of notes collateralized	50.00%
Two Remaining Promissory Notes | Employees And Former Employees
Class of Stock [Line Items]
Interest rate	2.30%