CONSOLIDATED INCOME STATEMENTS (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Sales	$ 290.8	$ 242.7	$ 832.4	$ 721.7
Cost of sales	159.6	135.9	465.0	400.8
Selling and administrative	34.5	27.3	94.2	76.6
Research and development	11.9	11.3	33.1	32.4
Business separation, restructuring and cost reduction actions	6.0	1.1	15.3	(1.6)
Other (income) expense, net	(2.2)	(0.3)	(5.2)	(2.4)
Operating Income (Loss)	81.0	67.4	230.0	215.9
Equity affiliates’ income	0.0	0.0	0.0	0.2
Interest expense	11.9	0.0	35.0	0.0
Income Before Income Taxes	69.1	67.4	195.0	216.1
Income tax provision	14.4	17.6	41.2	43.2
Net Income	54.7	49.8	153.8	172.9
Less: Net Income Attributable to Non-controlling Interests	2.0	2.0	5.4	6.1
Net Income Attributable to Versum	$ 52.7	$ 47.8	$ 148.4	$ 166.8
Net income attributable to Versum per common share:
Basic (usd per share)	$ 0.48	$ 0.44	$ 1.36	$ 1.54
Diluted (usd per share)	$ 0.48	$ 0.44	$ 1.36	$ 1.54
Shares used in computing per common share amounts:
Basic (shares)	108.8	108.7	108.7	108.7
Diluted (shares)	109.5	108.7	109.3	108.7