Business Separation, Restructuring, and Cost Reduction Actions (Narrative) (Details) $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Jan. 31, 2016 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($) position	Sep. 30, 2015 USD ($) position
Restructuring Cost and Reserve [Line Items]
Restructuring charge net of business separation costs										$ 4.7	$ (0.7)	$ 21.6
Number of positions eliminated | position											90	260
Carrying value of assets						$ 17.9					$ 17.9
Restructuring charge		$ 10.2	$ 6.0	$ 6.1	$ 3.2	$ 2.5	$ 1.1	$ (1.8)	$ (0.9)	25.5	0.9	$ 21.6
Operating Segments | Materials
Restructuring Cost and Reserve [Line Items]
Restructuring charge												12.3
Operating Segments | Delivery Systems and Services
Restructuring Cost and Reserve [Line Items]
Restructuring charge												5.8
Corporate, Non-Segment
Restructuring Cost and Reserve [Line Items]
Restructuring charge												3.5
Onsite Ammonia Plant
Restructuring Cost and Reserve [Line Items]
Gain from sale of plants								1.4
Proceeds from sale of plants	$ 17.1							$ 17.1
Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charge net of business separation costs										4.7	2.5	14.4
Asset actions
Restructuring Cost and Reserve [Line Items]
Restructuring charge net of business separation costs										$ 0.0	(3.2)	$ 7.2
Separation
Restructuring Cost and Reserve [Line Items]
Costs incurred from separation											$ 1.6