Summary of Significant Accounting Policies Change in Accounting Policies (Tables)

12 Months Ended

Sep. 30, 2018

Accounting Changes and Error Corrections [Abstract]

Accounting Changes [Text Block]

The following table summarizes the effect of this accounting change on the company’s consolidated statements of income for each of the years ended September 30, 2017 and 2016:

	As Originally Reported under LIFO		As Adjusted under FIFO		Effect of Change
(In millions, except per share data)
Year ended September 30, 2016
Cost of sales	$	539.5	$	542.2	$	2.7
Net income	219.9		217.2		(2.7		)
Net income attributable to Versum	212.0		209.3		(2.7		)
Net income attributable to Versum per common share:
Basic	$	1.95	$	1.93	$	(0.02	)
Diluted	$	1.95	$	1.93	$	(0.02	)
Year ended September 30, 2017
Cost of sales	$	636.9	$	636.4	$	(0.5	)
Income tax provision	52.8		53.0		0.2
Net income	199.9		200.2		0.3
Net income attributable to Versum	193.0		193.3		0.3
Net income attributable to Versum per common share:
Basic	$	1.78	$	1.78	$	—
Diluted	$	1.76	$	1.77	$	0.01