Acquisitions - Pro Forma Summary of All Acquisitions (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Business Combinations [Abstract]
Revenue	$ 13,193.4	$ 12,831.9
Net income	$ 280.2	$ 275.6
Basic net income per share (in dollars per share)	$ 12.07	$ 11.31
Diluted net income per share (in dollars per share)	$ 11.98	$ 11.26