Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Millions	Mar. 31, 2019	Sep. 30, 2018
Statement Of Financial Position [Abstract]
Accounts and notes receivable, reserve for doubtful accounts	$ 5	$ 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
Common stock, issued shares	58,644,974	60,566,375
Common stock, outstanding shares	58,449,603	60,366,569
Common treasury stock, shares	195,371	199,806