Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2015	Sep. 30, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 122	$ 128
Common stock, par value per share	$ 0.50	$ 0.50
Common stock, shares authorized	1,200,000,000	1,200,000,000
Common stock, shares issued	953,354,012	953,354,012
Common stock, shares outstanding	643,099,581	654,608,521
Treasury stock, shares	310,254,431	298,745,491