Share-based compensation and employee benefit plans - Reconciliation funded status and the net amounts recognized for the defined benefit plans (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)
Change in benefit obligation
Projected benefit obligation, beginning of year	$ 22.8
Service cost	1.0
Interest cost	0.2
Actuarial losses	(0.8)
Benefit payments	(0.5)
Tax payments	(0.1)
Currency revaluation effect	(2.2)
Projected benefit obligation, end of year	20.4
Change in plan assets
Fair value of plan assets, beginning of year	21.5
Employer contributions	0.5
Benefit payments	(0.3)
Interest income	3.3
Currency revaluation effect	(2.3)
Fair value of plan assets, end of year	22.7
Funded status at end of year	2.3
Defined Benefit Plan Disclosure [Line Items]
Funded status at end of year	2.3
Foreign Plan
Change in benefit obligation
Interest cost	0.0
Sweden
Change in plan assets
Funded status at end of year	6.0
Defined Benefit Plan Disclosure [Line Items]
Funded status at end of year	6.0
Germany
Change in plan assets
Funded status at end of year	(3.7)
Defined Benefit Plan Disclosure [Line Items]
Funded status at end of year	$ (3.7)