Goodwill and Other Intangible Assets - Summary of Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, accumulated amortization	$ (928.2)	$ (833.7)
Gross Value	1,920.0	1,896.3
Accumulated Amortization	(928.2)	(833.7)
Net Value	991.8	1,062.6
C&W trade name
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	546.0	546.0
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	1,356.9	1,333.1
Finite-lived intangible assets, accumulated amortization	(919.8)	(827.5)
Finite-lived intangible assets, net value	437.1	505.6
Accumulated Amortization	$ (919.8)	$ (827.5)
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (in years)	1 year	1 year
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (in years)	15 years	15 years
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 17.1	$ 17.2
Finite-lived intangible assets, accumulated amortization	(8.4)	(6.2)
Finite-lived intangible assets, net value	8.7	11.0
Accumulated Amortization	$ (8.4)	$ (6.2)
Other intangible assets | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (in years)	2 years	2 years
Other intangible assets | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (in years)	13 years	13 years