Post-Employment Plans - Net periodic pension cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net acquisitions/(disposals)	$ (1.3)	$ 0.0
Service costs	3.3	3.9	$ 2.7
Interest cost	2.7	2.6	2.8
Expected return on assets	(4.9)	(5.5)	(4.9)
Settlement	0.1	1.1	0.0
Curtailment	0.0	0.0	0.0
Net actuarial loss/(gain)	0.1	0.1	0.9
Net periodic pension cost/(gain)	1.3	2.2	1.5
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net acquisitions/(disposals)	0.0	0.0
Service costs	0.0	0.0	0.0
Interest cost	0.1	0.1	0.1
Expected return on assets	0.0	0.0	0.0
Settlement	0.0	0.0	0.0
Curtailment	0.0	0.0	0.0
Net actuarial loss/(gain)	(0.6)	(1.4)	(3.2)
Net periodic pension cost/(gain)	$ (0.5)	$ (1.3)	$ (3.1)