Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Millions	Jun. 30, 2018	Sep. 30, 2017
Statement Of Financial Position [Abstract]
Accounts and notes receivable, reserve for doubtful accounts	$ 9	$ 9
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
Common stock, issued shares	61,759,181	62,087,627
Common stock, outstanding shares	61,558,577	61,884,347
Common treasury stock, shares	200,604	203,280