CONSOLIDATED COMPREHENSIVE INCOME STATEMENTS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 52.3	$ 67.4
Other Comprehensive Income (Loss), net of tax
Translation adjustments, net	(30.1)	4.0
Pension activity, net of tax of $1.5 and $0	(5.5)	0.0
Total Other Comprehensive Income (Loss)	(35.6)	4.0
Comprehensive Income	16.7	71.4
Net Income Attributable to Non-controlling Interests	1.5	2.2
Other Comprehensive Income (Loss) Attributable to Non-controlling Interests	(1.0)	0.2
Comprehensive Income Attributable to Versum	$ 16.2	$ 69.0