Goodwill and Intangible Assets - Components of Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (in Years)	8 years 6 months	9 years 1 month 6 days
Gross Carrying Amount	$ 542.9	$ 542.9
Accumulated Amortization	$ 275.2	$ 247.0
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (in Years)	8 years 4 months 24 days	9 years 1 month 6 days
Gross Carrying Amount	$ 503.8	$ 503.8
Accumulated Amortization	$ 246.2	$ 220.2
Trademarks and Trade Names
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (in Years)	9 years 3 months 18 days	9 years 3 months 18 days
Gross Carrying Amount	$ 34.8	$ 34.8
Accumulated Amortization	$ 24.8	$ 23.0
Other Intangible Assets
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (in Years)	10 months 24 days	1 year 2 months 12 days
Gross Carrying Amount	$ 4.3	$ 4.3
Accumulated Amortization	$ 4.2	$ 3.8