Goodwill and Intangible Assets - Computer Software and Goodwill (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Computer software
Balance at beginning of period	$ 631.8	$ 557.4
Additions at cost	44.0	43.4
Amortization	(34.9)	(30.3)
Impairment / Write-off	(0.3)
Other	2.2	(7.1)
Balance at end of period	642.8	563.4
Goodwill
Balance at beginning of period	3,431.3	3,493.3
Amortization	0.0
Other	4.4	(17.9)
Balance at end of period	$ 3,435.7	$ 3,475.4