Intangible Assets - Changes in Carrying Value (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Finite-lived Intangible Assets [Roll Forward]
Gross Carrying Amount, Beginning Balance			$ 1,794.2
Accumulated Amortization, Beginning Balance			(668.8)
Net Carrying Amount, Beginning Balance			1,125.4
Customer relationships obtained from acquisition of business			50.6
Amortization expense	$ (31.9)	$ (30.9)	(94.4)	$ (92.7)
Gross Carrying Amount, Ending Balance	1,844.8		1,844.8
Accumulated Amortization, Ending Balance	(763.2)		(763.2)
Net Carrying Amount, Ending Balance	$ 1,081.6		$ 1,081.6