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Plant Closures (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Accelerated depreciation	$ 140	$ 136	$ 125
Completed Plant
Accelerated depreciation	140	136	125
Property, Plant, and Equipment, Owned, Accumulated Depreciation	482
Depreciation	1,800	$ 1,400	$ 1,600
Additional depreciation for coal-fired fleet
Completed Plant
Depreciation	$ 339
Property, Plant and Equipment [Member]
Completed Plant
Property, Plant and Equipment, Dispositions	22 million	4 million	13 million

X

- Definition

Accelerated depreciation

+ References

No definition available.

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- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

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- References

No definition available.

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- Definition

Describes an entity's accounting treatment for disposals of property, plant and equipment, including gains and losses related thereto.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section S99
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=27011434&loc=d3e125663-122742

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

The cumulative amount of depreciation (related to long-lived, depreciable flight assets owned by the entity and used in the entity's principle business operations and capitalized assets classified as property, plant and equipment that are owned by the entity) that has been recognized in the income statement.

+ References

No definition available.

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