ANNUAL CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY AND NONCONTROLLING INTERESTS - USD ($) $ in Millions	Total	Common Stock	Capital in Excess of Par	Accumulated Deficit	Air Products’ Net Investment	Accumulated Other Comprehensive Income (Loss)	Total Versum’s Stockholders’ Equity (Deficit)	Non-controlling Interests
Stockholders' equity, beginning balance at Sep. 30, 2014	$ 873.4	$ 0.0	$ 0.0	$ 0.0	$ 822.5	$ 13.5	$ 836.0	$ 37.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	191.2			0.0	184.1		184.1	7.1
Net transfers to Air Products	(270.4)				(269.8)		(269.8)	(0.6)
Other comprehensive income (loss)	(48.4)					(46.3)	(46.3)	(2.1)
Other Comprehensive Income (Loss), Net of Tax	(48.4)
Share-based compensation	4.7				4.7		4.7
Dividends to non-controlling interests	(9.8)							(9.8)
Stockholders' equity, ending balance at Sep. 30, 2015	740.7	0.0	0.0	0.0	741.5	(32.8)	708.7	32.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	219.9			0.0	212.0		212.0	7.9
Net transfers to Air Products	(1,084.2)				(1,085.8)		(1,085.8)	1.6
Other comprehensive income (loss)	22.8					22.8	22.8	0.0
Other Comprehensive Income (Loss), Net of Tax	22.8
Share-based compensation	5.0				5.0		5.0
Dividends to non-controlling interests	(7.6)							(7.6)
Stockholders' equity, ending balance at Sep. 30, 2016	(103.4)	0.0	0.0	0.0	(127.3)	(10.0)	(137.3)	33.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	199.9			193.0	0.0		193.0	6.9
Net transfers to Air Products	(165.1)			(298.2)	135.4	(2.4)	(165.2)	0.1
Reclassification of Air Products' net investment to additional paid in capital			8.1		(8.1)
Cash dividend paid	(10.9)		(10.9)				(10.9)
Issuance of common stock at separation	108.7	108.7					108.7
Issuance of common stock through shared based compensation plans	0.1	0.1					0.1
Other comprehensive income (loss)	(4.7)					(6.0)	(6.0)
Other Comprehensive Income (Loss), Net of Tax	(7.1)							1.3
Share-based compensation	7.6		7.6				7.6
Dividends to non-controlling interests	(7.6)							(7.6)
Stockholders' equity, ending balance at Sep. 30, 2017	$ 24.6	$ 108.8	$ 4.8	$ (105.2)	$ 0.0	$ (18.4)	$ (10.0)	$ 34.6