Benefit Plans - Pension Plans with Accumulated Benefit Obligations (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Retirement Benefits [Abstract]
Accumulated benefit obligation exceeds the fair value of plan assets, projected benefit obligation	$ 2,140	$ 2,104
Projected benefit obligation exceeds the fair value of plan assets, projected benefit obligation	2,159	2,182
Accumulated benefit obligation exceeds the fair value of plan assets, accumulated benefit obligation	2,088	2,059
Accumulated benefit obligation exceeds the fair value of plan assets, fair value of plan assets	1,575	1,644
Projected benefit obligation exceeds the fair value of plan assets, fair value of plan assets	$ 1,591	$ 1,720

No definition available.

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- Definition

Amount of plan asset for defined benefit pension plan with projected benefit obligation in excess of plan assets.

+ References

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- Definition

Amount of projected benefit obligation for defined benefit pension plan with projected benefit obligation in excess of plan assets.

+ References

+ Details

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- Definition

Amount of accumulated benefit obligation for defined benefit plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480482/715-20-55-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-3

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- Definition

Amount of plan asset for defined benefit plan with accumulated benefit obligation in excess of plan assets.

+ References

+ Details

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- Definition

Amount of projected benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-3

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