Segment and Geographic Information - Sales by Product Group (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Revenue, Major Customer [Line Items]
Sales	$ 248.4	$ 242.7	$ 233.5	$ 245.5	$ 232.4	$ 263.0	$ 258.8	$ 255.1	$ 970.1	$ 1,009.3	$ 942.5
Process Materials
Revenue, Major Customer [Line Items]
Sales									387.4	387.3	321.8
Advanced Materials
Revenue, Major Customer [Line Items]
Sales									369.3	356.1	318.2
Equipment and Installations
Revenue, Major Customer [Line Items]
Sales									150.8	208.3	244.1
Site Services
Revenue, Major Customer [Line Items]
Sales									$ 62.6	$ 57.6	$ 58.4