Defined benefit and 401(k) savings plan - Swiss Plan Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Retirement Benefits [Abstract]
Pension expense	$ 0.8	$ 2.0	$ 2.4
Change in Plan Assets:
Fair value of plan assets, beginning of period	29.3	27.6
Employer contributions	1.5	1.4
Employee contributions	0.9	0.9
Net benefits received	3.4	0.5
Actual return on plan assets	(0.4)	(0.1)
Settlements	(5.0)	0.0
Currency impact	(0.4)	(1.0)
Fair value of plan assets, end of period	29.3	29.3	27.6
Change in Benefit Obligation:
Projected benefit obligation, beginning of period	46.8	49.2
Service cost	1.9	2.4	1.9
Interest Cost	0.1	0.0	0.1
Employee contributions	0.9	0.9
Actuarial gain	(10.0)	(4.6)
Net benefits received	3.4	0.5
Settlements	(5.0)	0.0
Currency impact	(0.9)	(1.6)
Projected benefit obligation, end of period	37.2	46.8	$ 49.2
Funded status, end of period	(7.9)	(17.5)
Accumulated benefit obligation, end of period	$ 34.0	$ 41.8