Consolidated Statements of Comprehensive Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Net Income (Loss) Attributable to Parent [Abstract]
Sales	$ 2,285	$ 2,084	$ 1,929
Cost of sales	1,479	1,308	1,181
Gross profit	806	776	748
Selling, general and administrative expenses	430	396	365
Legacy and separation-related expenses, net	14	11	6
Equity and other income, net	(33)	(25)	(19)
Operating income	395	394	396
Net pension and other postretirement plan income	0	(138)	(35)
Net interest and other financing expenses	63	42	9
Net loss on acquisition	0	0	1
Income before income taxes	332	490	421
Income tax expense	166	186	148
Net income	$ 166	$ 304	$ 273
NET INCOME PER SHARE
Net income per share, basic (usd per share)	$ 0.84	$ 1.49	$ 1.60
Net income per share, diluted (usd per share)	$ 0.84	$ 1.49	$ 1.60
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING
Weighted average common shares outstanding, basic (in shares)	197	204	170
Weighted average common shares outstanding, diluted (in shares)	197	204	170
Dividends paid per common share (usd per share)	$ 0.298	$ 0.196	$ 0.00
COMPREHENSIVE INCOME
Net income	$ 166	$ 304	$ 273
Other comprehensive (loss) income, net of tax
Currency translation adjustments	(10)	7	8
Amortization of pension and other postretirement plan prior service credit	(9)	(8)	(1)
Other comprehensive (loss) income	(19)	(1)	7
Comprehensive income	$ 147	$ 303	$ 280