Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 299.7	$ 166.9
Accumulated Amortization	(70.8)	(61.2)
Net Carrying Amount	228.9	105.7
Amortization of intangible assets	17.7	8.4	$ 3.6
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
2019	20.5
2020	19.9
2021	19.5
2022	18.2
2023	17.5
Indefinite-lived trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7.9	7.9
Accumulated Amortization	0.0	0.0
Net Carrying Amount	7.9	7.9
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	259.9	137.5
Accumulated Amortization	(58.9)	(51.9)
Net Carrying Amount	$ 201.0	85.6
Weighted-average amortization period	12 years 8 months 12 days
Finite-lived trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 20.3	8.4
Accumulated Amortization	(3.8)	(2.3)
Net Carrying Amount	$ 16.5	6.1
Weighted-average amortization period	7 years
Amortization of intangible assets	$ 17.7	8.4
Other contract-related assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5.7	6.6
Accumulated Amortization	(3.1)	(3.0)
Net Carrying Amount	$ 2.6	3.6
Weighted-average amortization period	5 years 8 months 12 days
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 5.9	6.5
Accumulated Amortization	(5.0)	(4.0)
Net Carrying Amount	$ 0.9	$ 2.5
Weighted-average amortization period	1 year 7 months 6 days