Debt and Financing Arrangements - Components of Net Financing Charges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Debt Disclosure [Abstract]
Interest expense, net of capitalized interest costs	$ 110	$ 115	$ 328	$ 343
Banking fees and bond cost amortization	14	14	41	55
Interest income	(10)	(4)	(24)	(16)
Net foreign exchange results for financing activities	(13)	(1)	(13)	(6)
Net financing charges	$ 101	$ 124	$ 332	$ 376