Debt and Financing Arrangements - Components of Net Financing Charges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Debt Disclosure [Abstract]
Interest expense, net of capitalized interest costs	$ 97	$ 99	$ 188	$ 201
Banking fees and bond cost amortization	7	8	13	15
Interest income	(6)	(1)	(13)	(8)
Net foreign exchange results for financing activities	0	1	(5)	1
Net financing charges	$ 98	$ 107	$ 183	$ 209