Deferred Costs, Capitalized, Prepaid, and Other Assets (Policies)	9 Months Ended
Jun. 30, 2025
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Derivatives, Methods of Accounting, Hedging Derivatives	Commodity Contract Derivative Assets. See Note 14 — Risk Management Activities and Derivative Transactions — Derivatives Not Receiving Hedge Accounting Treatment — Commodity Derivatives and — Commodity Derivatives under the FHP for a discussion of TVA's commodity contract derivatives.

Disclosure of accounting policy for derivatives used in hedging relationships, which may include how gains or losses are recognized and presented in the financial statements, and amortization policies for deferred amounts.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 25
-Name Accounting Standards Codification
-Section 40
-Paragraph 8A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480270/815-25-40-8A

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EEEE
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4EEEE

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