Goodwill and Intangible Assets - Schedule of Computer Software and Goodwill (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023
Computer software
Balance at beginning of period	$ 684.7	$ 671.4	$ 666.3	$ 656.7	$ 642.8	$ 631.8
Additions at cost	55.4	54.9	52.5	39.8	52.2	44.0
Amortization	(44.8)	(41.4)	(40.7)	(39.5)	(37.4)	(34.9)
Impairment / Write-off		(0.2)			(0.9)	(0.3)
Other	9.1	0.0	(6.7)	(6.1)	0.0	2.2
Balance at end of period	704.4	684.7	671.4	650.9	656.7	642.8
Goodwill
Balance at beginning of period	3,426.6	3,424.7	3,445.8	3,422.4	3,435.7	3,431.3
Other	20.9	1.9	(21.1)	(8.5)	(13.3)	4.4
Balance at end of period	$ 3,447.5	$ 3,426.6	$ 3,424.7	$ 3,413.9	$ 3,422.4	$ 3,435.7