Business Acquisitions Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2015	Jun. 30, 2015	Jun. 30, 2014
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired		$ 127.0	$ 147.3
Goodwill recognized through acquisitions		40.7
Goodwill, purchase accounting adjustments		$ 0.2
Acme
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired	$ 67.6
Intangible assets	30.8
Goodwill recognized through acquisitions	$ 21.1
Weighted average useful life	20 years
Turner
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired	$ 37.6
Intangible assets	22.0
Goodwill recognized through acquisitions	$ 11.8
Weighted average useful life	19 years
EC&M
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired	$ 21.6
Intangible assets	8.5
Goodwill recognized through acquisitions	$ 7.8
Weighted average useful life	16 years