Goodwill and Intangible Assets - Goodwill Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill
Beginning Balance, Goodwill	$ 459.7	$ 208.9
Foreign currency translation adjustments and other	(1.6)	2.5
Goodwill acquired during the year	67.9	248.3
Purchase price adjustment	(5.3)
Ending Balance, Goodwill	520.7	459.7
Goodwill Impaired
Beginning Balance, accumulated goodwill impairment loss	147.1	147.1
Ending Balance, accumulated goodwill impairment loss	147.1	147.1
Energy & Chemicals
Goodwill
Beginning Balance, Goodwill	275.1	27.9
Foreign currency translation adjustments and other	(1.1)	0.1
Goodwill acquired during the year	27.1	247.1
Purchase price adjustment	(5.3)
Ending Balance, Goodwill	295.8	275.1
Goodwill Impaired
Beginning Balance, accumulated goodwill impairment loss	64.4	64.6
Ending Balance, accumulated goodwill impairment loss	64.4	64.4
D&S West
Goodwill
Beginning Balance, Goodwill	147.3	146.2
Foreign currency translation adjustments and other	(0.7)	(0.1)
Goodwill acquired during the year	4.7	1.2
Purchase price adjustment	0.0
Ending Balance, Goodwill	151.3	147.3
Goodwill Impaired
Beginning Balance, accumulated goodwill impairment loss	82.5	82.5
Ending Balance, accumulated goodwill impairment loss	82.5	82.5
D&S East
Goodwill
Beginning Balance, Goodwill	37.3	34.8
Foreign currency translation adjustments and other	0.2	2.5
Goodwill acquired during the year	36.1	0.0
Purchase price adjustment	0.0
Ending Balance, Goodwill	73.6	37.3
Goodwill Impaired
Beginning Balance, accumulated goodwill impairment loss	0.0	0.0
Ending Balance, accumulated goodwill impairment loss	$ 0.0	$ 0.0