Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Millions	Dec. 31, 2018		Sep. 30, 2018
Statement Of Financial Position [Abstract]
Accounts and notes receivable, reserve for doubtful accounts	$ 6		$ 7
Preferred stock, authorized shares	2,000,000		2,000,000
Preferred stock, par value	$ 1		$ 1
Preferred stock, Issued shares	0		0
Preferred stock, Outstanding shares	0		0
Common stock, authorized shares	200,000,000		200,000,000
Common stock, par value	$ 1	[1]	$ 1
Common stock, issued shares	59,709,462		60,566,375
Common stock, outstanding shares	59,509,656		60,366,569
Common treasury stock, shares	199,806		199,806

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