Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2019	Jun. 30, 2019
Goodwill
Beginning Balance, Goodwill	$ 520.7	$ 520.7
Foreign currency translation adjustments		(0.6)
Goodwill purchase price adjustment		22.5
Ending Balance, Goodwill		542.6
Beginning Balance, Accumulated goodwill impairment loss	147.1	147.1
Ending Balance, Accumulated goodwill impairment loss		147.1
VRV
Goodwill
Beginning Balance, Goodwill	63.2	63.2
Goodwill purchase price adjustment		21.7
Ending Balance, Goodwill		84.9
Skaff
Goodwill
Goodwill purchase price adjustment	0.8	0.8
Energy & Chemicals
Goodwill
Beginning Balance, Goodwill	295.8	295.8
Foreign currency translation adjustments		0.2
Ending Balance, Goodwill		305.8
Beginning Balance, Accumulated goodwill impairment loss	64.6	64.6
Ending Balance, Accumulated goodwill impairment loss		64.6
Energy & Chemicals | VRV
Goodwill
Goodwill purchase price adjustment		9.8
D&S West
Goodwill
Beginning Balance, Goodwill	151.3	151.3
Foreign currency translation adjustments		0.0
Goodwill purchase price adjustment		0.8
Ending Balance, Goodwill		152.1
Beginning Balance, Accumulated goodwill impairment loss	82.5	82.5
Ending Balance, Accumulated goodwill impairment loss		82.5
D&S East
Goodwill
Beginning Balance, Goodwill	73.6	73.6
Foreign currency translation adjustments		(0.8)
Ending Balance, Goodwill		84.7
Beginning Balance, Accumulated goodwill impairment loss	$ 0.0	0.0
Ending Balance, Accumulated goodwill impairment loss		0.0
D&S East | VRV
Goodwill
Goodwill purchase price adjustment		$ 11.9