Debt and Financing Arrangements - Components of Net Financing Charges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Debt Disclosure [Abstract]
Interest expense, net of capitalized interest costs	$ 53	$ 62	$ 112	$ 124
Banking fees and bond cost amortization	4	5	12	10
Interest income	(3)	(5)	(6)	(18)
Net foreign exchange results for financing activities	(10)	(3)	(15)	(5)
Net financing charges	$ 44	$ 59	$ 103	$ 111