Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021
Regulatory Assets and Liabilities
Current regulatory assets	$ 163	$ 196
Non-current regulatory assets	7,793	7,956
Regulatory assets	7,956	8,152
Current regulatory liabilities	223	340
Regulatory Liability, Noncurrent	25	40
Regulatory Liabilities	248	380
Fuel cost adjustment tax equivalents
Regulatory Assets and Liabilities
Current regulatory liabilities	137	130
Unrealized gains/losses on commodity derivatives
Regulatory Assets and Liabilities
Current regulatory liabilities	86	210
Regulatory Liability, Noncurrent	25	40
Unrealized losses on interest rate derivatives [Member]
Regulatory Assets and Liabilities
Current regulatory assets	109	114
Non-current regulatory assets	1,143	1,122
Unrealized gains/losses on commodity derivatives
Regulatory Assets and Liabilities
Current regulatory assets	5	3
Non-current regulatory assets	1	0
Fuel cost adjustment receivable/liability
Regulatory Assets and Liabilities
Current regulatory assets	49	79
Pension Costs [Member]
Regulatory Assets and Liabilities
Non-current regulatory assets	3,592	3,668
Nuclear desommissioning costs [Member]
Regulatory Assets and Liabilities
Non-current regulatory assets	218	363
Non-nuclear decommissioning [Member]
Regulatory Assets and Liabilities
Non-current regulatory assets	2,696	2,653
Other non-current regulatory assets [Member]
Regulatory Assets and Liabilities
Non-current regulatory assets	$ 143	$ 150

Regulatory Assets and Liabilities [Line Items]

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- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost.

+ References

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- Definition

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

+ References

+ Details

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- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 405
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

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- Definition

The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period.

+ References

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- Definition

The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.24)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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