Stockholders' Deficit - Schedule of Changes in Stockholders' Deficit (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance as of September 30, 2017			$ (117)
Net income	$ 64	$ 56	121	$ 199
Repurchases of common stock			(224)
Stock-based compensation plans			7
Dividends paid, $0.2235 per common share			(45)
Purchase of remaining ownership interest in subsidiary			(14)
Accumulated other comprehensive loss, net of tax:
Unrealized currency translation loss	(13)	6	(9)	3
Amortization of pension and other postretirement prior service credits in income	(3)	$ (2)	(7)	$ (6)
Balance as of June 30, 2018	$ (288)		$ (288)
Dividend per share (usd per share)			$ 0.2235
Repurchase of common stock (shares)			10,000,000

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