Share-based compensation - Restricted stock units (Details) - Restricted stock units - USD ($) $ / shares in Units, $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Restricted stock (in units)
Outstanding, beginning of period (in shares)	1,293,107	1,293,107	36,520	25,520
Granted (in shares)	413,234	6,339,974	1,317,719	36,520
Vested (in shares)		(530,032)	(36,520)	(25,520)
Forfeited (in shares)		(212,111)	(24,612)	0
Outstanding, end of period (in shares)		6,890,938	1,293,107	36,520
Weighted-Average Grant Date Fair Value (per share)
Outstanding, beginning of period (in dollars per share)	$ 26.34	$ 26.34	$ 12.60	$ 5.87
Granted (in dollars per share)		32.51	26.33	12.60
Vested (in dollars per share)		30.57	12.60	5.87
Forfeited (in dollars per share)		29.74	26.00	0
Outstanding, end of period (in dollars per share)		$ 31.59	$ 26.34	$ 12.60
Unrecognized compensation expense, RSUs		$ 197.1
Weighted average period over which unrecognized compensation expense would be recognized		3 years 6 months
Fair value of RSUs vested		$ 16.2	$ 0.5	$ 0.2
Tranche One
Weighted-Average Grant Date Fair Value (per share)
Percentage that vest		50.00%

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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Percentage of vesting of award under share-based payment arrangement.

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