Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 115	$ 112
Common stock, par value per share	$ 0.50	$ 0.50
Common stock, shares authorized	1,200.0	1,200.0
Common stock, shares issued	953.4	953.4
Common stock, shares outstanding	611.6	611.0
Treasury stock, shares	341.8	342.4