Employee benefit plans - changes to plan assets using unobservable inputs (Details) - Non-U.S. - Pension plans - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Changes to plan assets
Beginning balance	$ 182.8	$ 167.5
Currency translation	21.1	11.1
Ending balance	118.6	182.8
Level 3
Changes to plan assets
Beginning balance	41.4	38.3
Purchases	4.1	9.1
Actual returns	0.5	0.5
Settlements	(1.5)	(4.8)
Currency translation	(1.1)	(1.7)
Ending balance	$ 43.4	$ 41.4