Fair Value of Financial Assets and Liabilities - Consideration of Credit Risk Concentrations (Details) - Credit Concentration Risk $ in Millions	Sep. 30, 2025 USD ($) Counterparty
Derivative [Line Items]
Significant counterparties	4
Municipal or cooperative electric entities or other utilities
Derivative [Line Items]
Significant counterparties	4
External credit rating, investment grade
Derivative [Line Items]
Significant counterparties	1
Credit exposure \| $	$ 4
Credit exposure, percentage	14.00%
Internal investment grade
Derivative [Line Items]
Significant counterparties	3
Credit exposure \| $	$ 21
Credit exposure, percentage	77.00%
External Credit Rating, Non Investment Grade [Member]
Derivative [Line Items]
Significant counterparties	0

Number of the entity's most significant counterparties for wholesale, trading and non-trading commodity activities with credit exposure.

No definition available.

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- Definition

Percentage of wholesale, trading and non-trading commodity credit exposure for the entity's most significant counterparties.

+ References

No definition available.

+ Details

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- Definition

Wholesale, trading and non-trading commodity credit exposure for the entity's most significant counterparties.

+ References

No definition available.

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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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 20
-Name Accounting Standards Codification
-Section 25
-Paragraph 6A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480682/815-20-25-6A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-5

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