Supplemental Financial Data - Computer Software and Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Computer software
Balance at beginning of period	$ 631.8	$ 557.4
Acquisitions		0.0
Additions at cost	182.4	220.1
Amortization	(153.7)	(124.4)
Impairment / Write-off	(2.3)	(1.3)
Other	8.1	(20.0)
Balance at end of period	666.3	631.8
Goodwill
Balance at beginning of period	3,431.3	3,493.3
Acquisition		1.3
Impairment / Write-off	0.0	0.0
Other	14.5	(63.3)
Balance at end of period	$ 3,445.8	$ 3,431.3