Acquisitions (Pro Forma Summary of All Acquisitions) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Business Combinations [Abstract]
Revenue	$ 3,745.3	$ 3,738.3	$ 10,000.7	$ 10,548.8
Net income	$ 160.1	$ 92.3	$ 291.9	$ 220.4
Basic net income per share (in dollars per share)	$ 7.01	$ 3.97	$ 12.71	$ 9.50
Diluted net income per share (in dollars per share)	$ 6.92	$ 3.94	$ 12.58	$ 9.44