Business Acquisitions - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired			$ 163.4	$ 183.8	$ 96.5
Goodwill acquired			55.3	$ 80.9
Payment to settle the net working capital adjustment			$ 0.2
Acme
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired		$ 67.4
Intangible assets acquired		30.8
Goodwill acquired		$ 21.6
Intangible assets, weighted average useful life		20 years
Turner
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired		$ 37.7
Intangible assets acquired		22.0
Goodwill acquired		$ 12.0
Intangible assets, weighted average useful life		19 years
EC&M
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired		$ 21.6
Intangible assets acquired		8.5
Goodwill acquired		$ 7.9
Intangible assets, weighted average useful life		16 years
GasBreaker
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired	$ 36.5
Intangible assets acquired	20.4
Goodwill acquired	$ 13.8
Intangible assets, weighted average useful life	17 years