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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Business Combinations [Abstract]
Beginning balance	$ 250.9	$ 257.6	$ 291.0	$ 259.0
Additions to estimated acquisition earn-out payables	6.1	10.1	16.9	25.1
Payments for estimated acquisition earn-out payables	(19.6)	(24.5)	(66.5)	(40.0)
Subtotal	237.4	243.2	241.4	244.1
Net change in earnings from estimated acquisition earn-out payables:
Change in fair value on estimated acquisition earn-out payables	(4.7)	(3.3)	(9.5)	(6.0)
Interest expense accretion	1.7	1.7	3.1	3.5
Net change in earnings from estimated acquisition earn-out payables	(3.0)	(1.6)	(6.4)	(2.5)
Foreign currency translation adjustments during the year	(1.5)	0.4	(2.1)	0.4
Ending balance	$ 232.9	$ 242.0	$ 232.9	$ 242.0