Contingencies - Summary of Environmental Reserves (Details) $ in Millions	9 Months Ended
Jun. 30, 2020 USD ($)
Environmental Reserves
Beginning balance	$ 15
Payments and other	(4)
Accruals	5
Ending balance	16
Superfund Sites
Environmental Reserves
Beginning balance	11
Payments and other	(3)
Accruals	4
Ending balance	12
Non-Superfund Sites
Environmental Reserves
Beginning balance	4
Payments and other	(1)
Accruals	1
Ending balance	$ 4

Total costs accrued as of the balance sheet date for environmental loss contingencies.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14326-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 25
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant