Goodwill and Intangible Assets - Computer Software and Goodwill (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Computer software
Balance at beginning of period	$ 666.3	$ 631.8
Additions at cost	52.5	44.0
Amortization	(40.7)	(34.9)
Impairment / Write-off		(0.3)
Other	(6.7)	2.2
Balance at end of period	671.4	642.8
Goodwill
Balance at beginning of period	3,445.8	3,431.3
Other	(21.1)	4.4
Balance at end of period	$ 3,424.7	$ 3,435.7