ANNUAL COMBINED INCOME STATEMENTS - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Sales	$ 970.1	$ 1,009.3	$ 942.5
Cost of sales	539.5	616.5	638.9
Selling and administrative	109.8	109.6	109.5
Research and development	43.9	40.7	38.4
Business separation, restructuring and cost reduction actions	0.9	21.6	1.3
Other income (expense), net	2.9	1.1	6.8
Operating Income	278.9	222.0	161.2
Equity affiliates’ income	0.2	1.0	1.7
Interest expense	0.4	0.1	0.3
Income Before Taxes	278.7	222.9	162.6
Income tax provision	58.8	31.7	31.9
Net Income	219.9	191.2	130.7
Less: Net Income Attributable to Non-controlling Interests	7.9	7.1	7.1
Net Income Attributable to Versum	$ 212.0	$ 184.1	$ 123.6
Net income attributable to Versum per common share:
Basic and diluted (usd per share)	$ 1.95	$ 1.69	$ 1.14
Shares used in computing per common share amounts:
Basic and diluted (shares)	108.7	108.7	108.7