Restructuring Activities - Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restructuring Reserve
Beginning balance, restructuring accrual	$ 0.9	$ 2.7
Restructuring costs	7.4	0.9
Property, plant and equipment impairment and disposals	(4.9)
Cash payments and other	(1.3)	(2.0)
Ending balance, restructuring accrual	1.9	1.6
Operating Segments | Energy & Chemicals
Restructuring Reserve
Beginning balance, restructuring accrual	0.0	0.2
Restructuring costs	4.5	0.2
Property, plant and equipment impairment and disposals	(3.2)
Cash payments and other	(0.6)	(0.2)
Ending balance, restructuring accrual	0.7	0.2
Operating Segments | D&S West
Restructuring Reserve
Beginning balance, restructuring accrual	0.0	1.2
Restructuring costs	0.3	0.0
Property, plant and equipment impairment and disposals	0.0
Cash payments and other	0.0	(1.2)
Ending balance, restructuring accrual	0.3	0.0
Operating Segments | D&S East
Restructuring Reserve
Beginning balance, restructuring accrual	0.8	0.2
Restructuring costs	2.4	0.2
Property, plant and equipment impairment and disposals	(1.7)
Cash payments and other	(0.5)	(0.4)
Ending balance, restructuring accrual	0.8	0.0
Corporate
Restructuring Reserve
Beginning balance, restructuring accrual	0.1	1.1
Restructuring costs	0.2	0.5
Property, plant and equipment impairment and disposals	0.0
Cash payments and other	(0.2)	(0.2)
Ending balance, restructuring accrual	$ 0.1	$ 1.4