Goodwill and Intangible Assets - Computer Software and Goodwill (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Computer software
Balance at beginning of period	$ 557.4	$ 437.0
Acquisitions	0.0	65.0
Additions at cost	43.4	42.2
Amortization	(30.3)	(24.5)
Write-off		(3.1)
Other	(7.1)	(8.5)
Balance at end of period	563.4	508.1
Goodwill
Balance at beginning of period	3,493.3	2,857.9
Acquisitions	0.5	488.4
Other	(18.4)	(28.1)
Balance at end of period	$ 3,475.4	$ 3,318.2