CONSOLIDATED INCOME STATEMENTS (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Sales	$ 270.8	$ 245.5
Cost of sales	150.9	132.4
Selling and administrative	30.2	23.6
Research and development	10.3	10.9
Business separation, restructuring and cost reduction actions	3.2	(0.9)
Other (income) expense, net	(2.9)	(1.1)
Operating Income	79.1	80.6
Equity affiliates’ income	0.0	0.2
Interest expense	11.5	0.0
Income Before Income Taxes	67.6	80.8
Income tax provision	15.3	13.4
Net Income	52.3	67.4
Less: Net Income Attributable to Non-controlling Interests	1.5	2.2
Net Income Attributable to Versum	$ 50.8	$ 65.2
Net income attributable to Versum per common share:
Basic (usd per share)	$ 0.47	$ 0.60
Diluted (usd per share)	$ 0.47	$ 0.60
Shares used in computing per common share amounts:
Basic (shares)	108.7	108.7
Diluted (shares)	109.2	108.7