Debt and Financing Arrangements Net Financing Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Debt Disclosure [Abstract]
Interest expense, net of capitalized interest costs	$ 240	$ 335	$ 409
Bank fees and bond cost amortization	26	28	30
Gain (Loss) on Extinguishment of Debt	0	60	0
Interest income	(23)	(61)	(13)
Net foreign exchange results for financing activities	(12)	(12)	(25)
Net financing charges	$ 231	$ 350	$ 401