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, 2017		203
Balance at beginning of period at Sep. 30, 2017	$ (117)	$ 2	$ 5	$ (167)	$ 43
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(10)			(10)
Dividends paid	(15)			(15)
Stock-based compensation	2		2
Repurchases of common stock (shares)		(2)
Repurchases of common stock	(39)			(39)
Currency translation adjustments	1				1
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	(14)		(7)	(7)
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, 2017		201
Balance at end of period at Dec. 31, 2017	(194)	$ 2	0	(238)	42
Common stock outstanding, at beginning of period (shares) at Sep. 30, 2017		203
Balance at beginning of period at Sep. 30, 2017	(117)	$ 2	5	(167)	43
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	121
Currency translation adjustments	(9)
Amortization of pension and other postretirement prior service credits in income, net of tax	(7)
Common stock outstanding, at end of period (shares) at Jun. 30, 2018		193
Balance at end of period at Jun. 30, 2018	(288)	$ 2	6	(323)	27
Common stock outstanding, at beginning of period (shares) at Dec. 31, 2017		201
Balance at beginning of period at Dec. 31, 2017	(194)	$ 2	0	(238)	42
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	67			67
Dividends paid	(15)			(15)
Stock-based compensation	2		3	(1)
Repurchases of common stock (shares)		(4)
Repurchases of common stock	(87)			(87)
Currency translation adjustments	3				3
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 Mar. 31, 2018		197
Balance at end of period at Mar. 31, 2018	(226)	$ 2	3	(274)	43
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	64			64
Dividends paid	(15)			(15)
Stock-based compensation	3		3
Repurchases of common stock (shares)		(4)
Repurchases of common stock	(98)			(98)
Currency translation adjustments	(13)				(13)
Amortization of pension and other postretirement prior service credits in income, net of tax	(3)				(3)
Common stock outstanding, at end of period (shares) at Jun. 30, 2018		193
Balance at end of period at Jun. 30, 2018	$ (288)	$ 2	6	(323)	27
Common stock outstanding, at beginning of period (shares) at Sep. 30, 2018	188	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, 2018	188	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)	181
Currency translation adjustments	(1)
Amortization of pension and other postretirement prior service credits in income, net of tax	$ (7)
Common stock outstanding, at end of period (shares) at Jun. 30, 2019	188	188
Balance at end of period at Jun. 30, 2019	$ (252)	$ 2	13	(291)	24
Common stock outstanding, at beginning of period (shares) at Dec. 31, 2018		188
Balance at beginning of period at Dec. 31, 2018	(343)	$ 2	8	(379)	26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	63			63
Dividends paid	(20)			(20)
Stock-based compensation	2		2
Currency translation adjustments	2				2
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 Mar. 31, 2019		188
Balance at end of period at Mar. 31, 2019	(298)	$ 2	10	(336)	26
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	65			65
Dividends paid	(20)			(20)
Stock-based compensation	3		3
Currency translation adjustments	1				1
Amortization of pension and other postretirement prior service credits in income, net of tax	$ (3)				(3)
Common stock outstanding, at end of period (shares) at Jun. 30, 2019	188	188
Balance at end of period at Jun. 30, 2019	$ (252)	$ 2	$ 13	$ (291)	$ 24