Business Acquisitions Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2015	Sep. 30, 2014
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired			$ 163.3	$ 163.9
Goodwill recognized through acquisitions			54.5
Goodwill, purchase accounting adjustments			0.2
Acme
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired		$ 67.4
Intangible assets		30.8
Goodwill recognized through acquisitions		$ 21.2
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
GasBreaker
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired	$ 36.5
Intangible assets	20.4		$ 20.4
Goodwill recognized through acquisitions	$ 13.7
Weighted average useful life	17 years