Business Combinations - Additions, Payments, and Net Changes, as well as Interest Expense Accretion on Estimated Acquisition Earn-Out Payables (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Business Combinations [Abstract]
Beginning balance	$ 291.0	$ 258.9
Additions to estimated acquisition earn-out payables	10.8	15.0
Payments for estimated acquisition earn-out payables	(46.9)	(15.5)
Subtotal	254.9	258.4
Net change in earnings from estimated acquisition earn-out payables:
Change in fair value on estimated acquisition earn-out payables	(4.8)	(2.7)
Interest expense accretion	1.4	1.8
Net change in earnings from estimated acquisition earn-out payables	(3.4)	(0.9)
Foreign currency translation adjustments during the year	(0.6)
Ending balance	$ 250.9	$ 257.5