XML 180 R124.htm IDEA: XBRL DOCUMENT
v3.25.3

Commitments and Contingencies - Purchase Obligations (Details) $ in Millions | 12 Months Ended |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2025 USD ($) Units megawatts Megawatts | Sep. 30, 2024 USD ($) | Sep. 30, 2023 USD ($) | Sep. 30, 2031 USD ($) | Sep. 30, 2030 USD ($) | Sep. 30, 2029 USD ($) | Sep. 30, 2028 USD ($) | Sep. 30, 2027 USD ($) | Sep. 30, 2026 USD ($)
Obligations |  |  |  |  |  |  |  |  |
Megawatts provided under power purchase obligations | Megawatts | 5,938 |  |  |  |  |  |  |  |
Remaining terms of the agreements, high end of range | 23 years |  |  |  |  |  |  |  |
Megawatts provided under transmission obligations | megawatts | 3,750 |  |  |  |  |  |  |  |
Power purchased under agreement | $ | $ 696 | $ 519 | $ 355 |  |  |  |  |  |
Scenario, Forecast |  |  |  |  |  |  |  |  |
Obligations |  |  |  |  |  |  |  |  |
Unrecorded Unconditional Purchase Obligation, Including Lease Not yet Commenced, Total | $ |  |  |  | $ 242 | $ 162 | $ 162 | $ 162 | $ 162 | $ 162
Purchase Agreements Required by Federal Law |  |  |  |  |  |  |  |  |
Obligations |  |  |  |  |  |  |  |  |
Megawatts provided under power purchase obligations | Units | 281 |  |  |  |  |  |  |  |
Number of generation sources under PPAs | Units | 1,344 |  |  |  |  |  |  |  |

X
- Definition Number of megawatts provided under the power purchase obligations. + References No definition available. + Details
Name: | tve_MegawattsProvidedUnderPowerPurchaseObligations
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Megawatts provided under transmission obligations + References No definition available. + Details
Name: | tve_Megawattsprovidedundertransmissionobligations
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of generation sources under PPAs + References No definition available. + Details
Name: | tve_NumberOfGenerationSourcesUnderPPAs
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition The expense for power purchased under contractual power purchase obligations. + References No definition available. + Details
Name: | tve_PowerPurchasedUnderAgreement
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The high end of the range of remaining terms of the agreements. + References No definition available. + Details
Name: | tve_RemainingTermsOfThePowerPurchaseObligationsHighEndOfRange
Namespace Prefix: | tve_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- 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 No definition available. + Details
Name: | us-gaap_LongTermPurchaseCommitmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of unrecorded obligation to transfer funds in future for fixed or minimum amount or quantity of product and service at fixed or minimum price. Includes, but is not limited to, lease not yet commenced and take-or-pay and throughput contracts. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 440 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482648/440-10-50-4 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-3 + Details
Name: | us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=tve_PurchaseAgreementsRequiredByFederalLawMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |