Segment and Geographic Information - Segments (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Sales	$ 294.5	$ 290.8	$ 270.8	$ 270.8	$ 248.4	$ 242.7	$ 233.5	$ 245.5	$ 1,126.9	$ 970.1	$ 1,009.3
Operating Income (Loss)	70.1	81.0	69.9	79.1	63.0	67.4	67.9	80.6	300.1	278.9	222.0
Business separation, restructuring and cost reduction actions	(10.2)	(6.0)	(6.1)	(3.2)	(2.5)	(1.1)	1.8	0.9	(25.5)	(0.9)	(21.6)
Depreciation and Amortization									46.0	46.9	56.9
Equity Affiliates’ Income	0.0	$ 0.0	$ 0.0	$ 0.0	0.0	$ 0.0	$ 0.0	$ 0.2	0.0	0.2	1.0
Total Assets	1,246.8				1,043.8				1,246.8	1,043.8	887.4
Investment in Net Assets of and Advances to Equity Affiliates	0.0				0.0				0.0	0.0	12.5
Expenditures for Long-Lived Assets									64.0	35.8	22.1
Operating Segments
Segment Reporting Information [Line Items]
Operating Income (Loss)									325.6	279.8	243.6
Operating Segments | Materials
Segment Reporting Information [Line Items]
Sales									829.7	756.7	743.4
Operating Income (Loss)									274.4	252.3	213.7
Business separation, restructuring and cost reduction actions											(12.3)
Depreciation and Amortization									43.1	44.4	48.1
Total Assets	773.8				733.4				773.8	733.4	754.8
Investment in Net Assets of and Advances to Equity Affiliates	0.0				0.0				0.0	0.0	12.5
Expenditures for Long-Lived Assets									45.7	34.4	21.2
Operating Segments | Delivery Systems and Services
Segment Reporting Information [Line Items]
Sales									293.6	213.4	265.9
Operating Income (Loss)									71.7	50.8	49.1
Business separation, restructuring and cost reduction actions											(5.8)
Depreciation and Amortization									1.4	2.1	8.3
Total Assets	110.9				104.0				110.9	104.0	92.7
Expenditures for Long-Lived Assets									1.7	0.7	0.8
Operating Segments | Corporate
Segment Reporting Information [Line Items]
Sales									3.6	0.0	0.0
Operating Income (Loss)									(20.5)	(23.3)	(19.2)
Depreciation and Amortization									1.5	0.4	0.5
Total Assets	$ 362.1				$ 206.4				362.1	206.4	39.9
Expenditures for Long-Lived Assets									16.6	0.7	0.1
Segment Reconciling Items
Segment Reporting Information [Line Items]
Business separation, restructuring and cost reduction actions									$ (25.5)	$ (0.9)	$ (21.6)