Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2016	Sep. 30, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 120	$ 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	643,261,142	654,608,521
Treasury stock, shares	310,092,870	298,745,491