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Debt and Financing Arrangements - Long-term Debt (Details) - USD ($) $ in Millions		6 Months Ended
	May 29, 2017	Mar. 31, 2019	Sep. 30, 2018	Aug. 19, 2016
Debt Instrument [Line Items]
Capital lease obligations		$ 1	$ 2
Less: debt issuance costs		(35)	(32)
Gross long-term debt		3,374	3,424
Less: current portion		1	2
Net long-term debt		3,373	3,422
Revolving credit facility \| Term Loan A - LIBOR plus 1.75% due in 2021
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,200	1,200
Revolving credit facility \| Term Loan A - LIBOR plus 1.75% due in 2021 \| LIBOR
Debt Instrument [Line Items]
Basis spread (as percent)		1.75%
Unsecured debt \| 4.875% Notes due in 2026
Debt Instrument [Line Items]
Long-term debt, gross		$ 900	900
Interest rate (as percent)		4.875%		4.875%
Unsecured debt \| 3.50% Notes due in 2024
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,123	1,162
Interest rate (as percent)		3.50%		3.50%
Unsecured debt \| European Investment Bank Loan - EURIBOR plus 0.90% due in 2022
Debt Instrument [Line Items]
Long-term debt, gross		$ 185	$ 192
Unsecured debt \| European Investment Bank Loan - EURIBOR plus 0.90% due in 2022 \| EURIBOR
Debt Instrument [Line Items]
Basis spread (as percent)	0.90%	0.90%