Debt and Financing Arrangements - 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	$ 38	$ 36	$ 73	$ 70
Banking fees and debt issuance cost amortization	4	2	7	4
Interest income	(3)	(1)	(4)	(2)
Net foreign exchange	1	0	(1)	(2)
Net financing charges	$ 40	$ 37	$ 75	$ 70

Amount of amortization expense attributable to debt issuance costs.

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Amount of gain (loss) from the increase (decrease) in fair value of foreign currency derivatives and nonderivative instruments designated as fair value hedging instruments which were recognized in earnings, net of offsets by the gain (loss) on the hedged item to the extent that the fair value hedge was determined to be effective.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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The net amount of operating interest income (expense).

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Amount of interest income earned from interest bearing assets classified as other.

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