Schedule of quarterly financial information disclosure.

No definition available.

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- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109226348&loc=d3e2420-110228

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- Definition

Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

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- Definition

Amount charged against operating income increasing loss contingency liability, after adjustments to reduce previously estimated charges.

+ References

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

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Unaudited Quarterly Financial Information - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020
Respirator Liabilities [Member]
Schedule Of Quarterly Financial Information Disclosure [Line Items]
Respirator charge		$ 20
U.S. Defined Benefit Plans [Member]
Schedule Of Quarterly Financial Information Disclosure [Line Items]
Net deferred tax asset carge due to a valuation allowance increase	$ 228		$ 228
Marshall Mine [Member]
Schedule Of Quarterly Financial Information Disclosure [Line Items]
Loss on sale and asset impairment charge	$ 129		$ 129