Goodwill and Identifiable Assets (Acquired Intangible Assets) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Intangible assets subject to amortization:
Gross Carrying Amount	$ 569.1	$ 569.6
Accumulated Amortization	352.4	340.6
Net Carrying Amount	216.7	229.0
Intangible assets not subject to amortization:
Trademarks, Carrying Amount	258.9	258.9
Intangible Assets, Gross (Excluding Goodwill)	828.0	828.5
Intangible Assets, Net (Excluding Goodwill), Total	475.6	487.9
Customer and Contractual Relationships
Intangible assets subject to amortization:
Accumulated Amortization	233.4	222.9
Net Carrying Amount	207.5	218.4
Total
Other Finite-Lived Intangible Assets, Gross	$ 440.9	441.3
Customer and Contractual Relationships | Minimum [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	7 years 3 months 18 days
Customer and Contractual Relationships | Maximum [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	12 years 9 months 18 days
Contractor Relations
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	4 years
Intangible assets subject to amortization:
Accumulated Amortization	$ 71.0	71.0
Net Carrying Amount	0.1	0.2
Total
Other Finite-Lived Intangible Assets, Gross	71.1	71.2
Backlog
Intangible assets subject to amortization:
Accumulated Amortization	28.7	28.5
Net Carrying Amount	0.6	0.8
Total
Other Finite-Lived Intangible Assets, Gross	$ 29.3	29.3
Backlog | Minimum [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Backlog | Maximum [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	2 years 9 months 18 days
Noncompete Agreements
Intangible assets subject to amortization:
Accumulated Amortization	$ 19.3	18.2
Net Carrying Amount	8.5	9.6
Total
Other Finite-Lived Intangible Assets, Gross	$ 27.8	$ 27.8
Noncompete Agreements | Minimum [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	3 years
Noncompete Agreements | Maximum [Member]
Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years