Goodwill and Other Intangibles - Computer Software and Goodwill (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021		Mar. 31, 2020
Computer Software
Balance at beginning of period	$ 437.0	[1]	$ 382.2
Acquisitions	65.0		0.0
Additions at cost	42.2		18.2
Amortization	(24.5)		(16.0)
Write-off	(3.1)		(0.2)
Other	(8.5)		(4.9)
Balance at end of period	508.1		379.3
Goodwill
Balance at beginning of period	2,857.9	[1]	2,841.7
Acquisitions	488.4		10.7
Other	(28.1)		(3.7)
Balance at end of period	$ 3,318.2		$ 2,848.7

[1] See discussion in Note 1 - Basis of Presentation for further detail regarding the elimination of the International lag reporting.