Income Taxes - Summary of Temporary Differences of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions		Sep. 30, 2018	Sep. 30, 2017
Deferred tax assets
Foreign net operating loss carryforwards	[1]	$ 43	$ 69
Employee benefit obligations		31	47
Environmental, self-insurance and litigation reserves (net of receivables)		120	192
State net operating loss carryforwards (net of unrecognized tax benefits)	[2]	48	62
Compensation accruals		31	72
Credit carryforwards (net of unrecognized tax benefits)	[3]	10	26
Other items		33	47
Valuation allowances	[4]	(79)	(122)
Total deferred tax assets		237	393
Deferred tax liabilities
Goodwill and other intangibles	[5]	273	432
Property, plant and equipment		215	302
Unremitted earnings		0	6
Total deferred tax liabilities		488	740
Net deferred tax liability		$ (251)	$ (347)

[1] Gross net operating loss carryforwards of $141 million will expire in future years beyond 2020 or have no expiration.

[2] Apportioned net operating loss carryforwards generated of $1.1 billion will expire in future years as follows: $69 million in 2019, $82 million in 2020 and the remaining balance in other future years.

[3] Credit carryforwards consist primarily of foreign tax credits of $4 million expiring in future years beyond 2020, and miscellaneous tax credits that will expire in 2024 or other future years.

[4] Valuation allowances primarily relate to certain state and foreign net operating loss carryforwards.

[5] The total gross amount of goodwill as of September 30, 2018 expected to be deductible for tax purposes is $29 million.