Condensed Consolidated Statements of Stockholders' Deficit - USD ($) shares in Millions, $ in Millions	Total	Common stock	Paid-in capital	Retained deficit	Accumulated other comprehensive income
Common stock outstanding, at beginning of period (shares) at Sep. 30, 2018		188
Balance at beginning of period at Sep. 30, 2018	$ (358)	$ 2	$ 7	$ (399)	$ 32
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	53			53
Dividends paid	(20)			(20)
Stock-based compensation	1		1
Currency translation adjustments	(4)				(4)
Amortization of pension and other postretirement prior service credits in income, net of tax	(2)				(2)
Common stock outstanding, at end of period (shares) at Dec. 31, 2018		188
Balance at end of period at Dec. 31, 2018	$ (343)	$ 2	8	(379)	26
Common stock outstanding, at beginning of period (shares) at Sep. 30, 2019	188	188
Balance at beginning of period at Sep. 30, 2019	$ (258)	$ 2	13	(284)	11
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	73			73
Dividends paid	(21)			(21)
Stock-based compensation	3		3
Currency translation adjustments	8				8
Amortization of pension and other postretirement prior service credits in income, net of tax	$ (2)				(2)
Common stock outstanding, at end of period (shares) at Dec. 31, 2019	188	188
Balance at end of period at Dec. 31, 2019	$ (196)	$ 2	$ 16	(231)	$ 17
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of adoption of new leasing standard, net of tax | ASU 2014-09				$ 1