Contingencies - Summary of environmental reserves (Details) $ in Millions	6 Months Ended
Mar. 31, 2017 USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 13
Payments and other	(3)
Accruals	2
Ending balance	12
Superfund Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	2
Payments and other	0
Accruals	0
Ending balance	2
Non-Superfund Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	11
Payments and other	(3)
Accruals	2
Ending balance	$ 10

Amount of environmental claims paid in the current period, net of other adjustments.

No definition available.

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Balance Type:	debit
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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-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

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-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

+ Details

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- Definition

Increase (decrease) in the accrual for environmental loss contingencies during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 5.Y.Q2)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

+ Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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- Details

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- Details

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