Debt and Financing Arrangements - Components of Net Financing Charges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Debt Disclosure [Abstract]
Transactions costs related to debt exchange offers			$ 17
Interest expense, net of capitalized interest costs	$ 118	$ 65	228	$ 137
Banking fees and bond cost amortization	11	5	41	12
Interest income	(5)	(2)	(12)	(4)
Net foreign exchange results for financing activities	(8)	3	(5)	(8)
Net financing charges	$ 116	$ 71	$ 252	$ 137