XML 168 R98.htm IDEA: XBRL DOCUMENT
v3.24.3

Fair Value Measurements - Fair Value Measurements (Details) - USD ($) $ in Millions | Sep. 30, 2024 | Sep. 30, 2023
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Fair value | $ 64 | $ 52 |
Investments |  |  |
Government debt securities | 457 | 347 |
Corporate debt securities | 378 | 300 |
Mortgage and asset-backed securities | 43 | 36 |
Institutional mutual funds | 342 | 288 |
Forward debt securities contracts - asset | 11 | 11 |
Cash, Cash Equivalents, and Short-term Investments | 278 | 270 |
Private equity funds measured at net asset value | 738 | 583 |
Private real estate measured at net asset value | 432 | 387 |
Private credit measured at net asset value | 219 | 158 |
Commingled funds measured at net asset value | 1,300 | 1,135 |
Total investments | 4,968 | 4,123 |
Interest Rate Derivative Assets, at Fair Value | 0 | 4 |
Commodity contract derivatives | 7 | 33 |
Total | 4,975 | 4,160 |
Liabilities |  |  |
Currency swaps | 116 | 141 | [1]
Interest rate swaps | 840 | 662 |
Commodity contract derivatives | 5 | 2 |
Total | 1,122 | 991 |
Equity Securities, FV-NI, Noncurrent | 770 | 608 |
Derivative Liability, Subject to Master Netting Arrangement, after Offset | 1,122 | 991 |
Derivative Asset, Subject to Master Netting Arrangement, after Offset | 7 | 37 |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Cash, Cash Equivalents, and Short-term Investments | 278 | 270 |
Government debt securities reclassed |  | 104 |
Commodity Contract under FHP |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Fair value | (161) | (186) |
Liabilities |  |  |
Derivative Liability, Subject to Master Netting Arrangement, after Offset | 161 | 186 |
Derivative Asset, Subject to Master Netting Arrangement, after Offset | 0 | 0 |
Fair Value, Inputs, Level 1 |  |  |
Investments |  |  |
Government debt securities | 400 | 287 |
Corporate debt securities | 0 | 0 |
Mortgage and asset-backed securities | 0 | 0 |
Institutional mutual funds | 342 | 288 |
Forward debt securities contracts - asset | 0 | 0 |
Cash, Cash Equivalents, and Short-term Investments | 95 | 104 |
Private equity funds measured at net asset value | 0 | 0 |
Private real estate measured at net asset value | 0 | 0 |
Private credit measured at net asset value | 0 | 0 |
Commingled funds measured at net asset value | 0 | 0 |
Total investments | 1,607 | 1,287 |
Interest Rate Derivative Assets, at Fair Value | 0 | 0 |
Commodity contract derivatives | 0 | 0 |
Total | 1,607 | 1,287 |
Liabilities |  |  |
Currency swaps | 0 | 0 |
Interest rate swaps | 0 | 0 |
Commodity contract derivatives | 0 | 0 |
Total | 0 | 0 |
Equity Securities, FV-NI, Noncurrent | 770 | 608 |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Cash, Cash Equivalents, and Short-term Investments | 95 | 104 |
Fair Value, Inputs, Level 1 | Commodity Contract under FHP |  |  |
Liabilities |  |  |
Derivative Liability, Subject to Master Netting Arrangement, after Offset | 0 | 0 |
Fair Value, Inputs, Level 2 |  |  |
Investments |  |  |
Government debt securities | 57 | 60 |
Corporate debt securities | 378 | 300 |
Mortgage and asset-backed securities | 43 | 36 |
Institutional mutual funds | 0 | 0 |
Forward debt securities contracts - asset | 11 | 11 |
Cash, Cash Equivalents, and Short-term Investments | 183 | 166 |
Private equity funds measured at net asset value | 0 | 0 |
Private real estate measured at net asset value | 0 | 0 |
Private credit measured at net asset value | 0 | 0 |
Commingled funds measured at net asset value | 0 | 0 |
Total investments | 672 | 573 |
Interest Rate Derivative Assets, at Fair Value | 0 | 4 |
Commodity contract derivatives | 7 | 33 |
Total | 679 | 610 |
Liabilities |  |  |
Currency swaps | 116 | 141 |
Interest rate swaps | 840 | 662 |
Commodity contract derivatives | 5 | 2 |
Total | 1,122 | 991 |
Equity Securities, FV-NI, Noncurrent | 0 | 0 |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Cash, Cash Equivalents, and Short-term Investments | 183 | 166 |
Fair Value, Inputs, Level 2 | Commodity Contract under FHP |  |  |
Liabilities |  |  |
Derivative Liability, Subject to Master Netting Arrangement, after Offset | 161 | 186 |
Fair Value, Inputs, Level 3 |  |  |
Investments |  |  |
Government debt securities | 0 | 0 |
Corporate debt securities | 0 | 0 |
Mortgage and asset-backed securities | 0 | 0 |
Institutional mutual funds | 0 | 0 |
Forward debt securities contracts - asset | 0 | 0 |
Cash, Cash Equivalents, and Short-term Investments | 0 | 0 |
Private equity funds measured at net asset value | 0 | 0 |
Private real estate measured at net asset value | 0 | 0 |
Private credit measured at net asset value | 0 | 0 |
Commingled funds measured at net asset value | 0 | 0 |
Total investments | 0 | 0 |
Interest Rate Derivative Assets, at Fair Value | 0 | 0 |
Commodity contract derivatives | 0 | 0 |
Total | 0 | 0 |
Liabilities |  |  |
Currency swaps | 0 | 0 |
Interest rate swaps | 0 | 0 |
Commodity contract derivatives | 0 | 0 |
Total | 0 | 0 |
Equity Securities, FV-NI, Noncurrent | 0 | 0 |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Cash, Cash Equivalents, and Short-term Investments | 0 | 0 |
Fair Value, Inputs, Level 3 | Commodity Contract under FHP |  |  |
Liabilities |  |  |
Derivative Liability, Subject to Master Netting Arrangement, after Offset | $ 0 | $ 0 |
[1] | See Note 15 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.

X
- Definition The fair value measurements of investment funds comprised of multiple individual financial instruments that are measured at net asset value + References No definition available. + Details
Name: | tve_Commingledfundsmeasuredatnetassetvalue
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value as of the balance sheet date of firm obligations in physical commodity contracts (for example, agricultural products, metals and energy). + References No definition available. + Details
Name: | tve_Commoditycontractderivativeliabilitiesfairvaluedisclosure
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The fair value as of the balance sheet date of firm holdings in mortgages, residential mortgage backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the mortgage backed security) and asset-backed securities that are primarily paid from the cash flows of a discrete pool of receivables or other financial assets (such as credit-card receivables), either fixed or revolving, that by their terms convert into cash within a finite time period. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings. + References No definition available. + Details
Name: | tve_FinancialInstrumentsOwnedMortgagesResidentialMortgagebackedandAssetbackedSecuritiesatFairValue
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value as of the balance sheet date of forward contract derivative assets. + References No definition available. + Details
Name: | tve_ForwardContractDerivativeAssetatFairValue
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Government debt securities reclassed + References No definition available. + Details
Name: | tve_GovernmentDebtSecuritiesReclassed
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value measurements of institutional mutual funds that are classified based on their existing investment portfolio as of the measurement date. + References No definition available. + Details
Name: | tve_Institutionalmutualfunds
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Private credit measured at net asset value + References No definition available. + Details
Name: | tve_Privatecreditmeasuredatnetassetvalue
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value measurements of private partnerships measured at net asset value. Private partnership investments may include holdings of investments in private real estate, venture capital, buyout, mezzanine or subordinated debt, restructuring or distressed debt, and special situations through funds management by third-party managers. + References No definition available. + Details
Name: | tve_Privatepartnershipsmeasuredatnetassetvalue
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value measurements of private real estate funds measured at net asset value + References No definition available. + Details
Name: | tve_Privaterealestatemeasuredatnetassetvalue
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of asset recognized for present right to economic benefit. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 100 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-100 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_AssetsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(9)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_CashCashEquivalentsAndShortTermInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value, after effect of master netting arrangement, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and contract can be net settled by means outside contract or delivery of asset. Includes derivative subject to master netting arrangement not elected or qualified to offset. Excludes derivative not subject to master netting arrangement or similar agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483466/210-20-50-3 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 22 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483444/210-20-55-22 + Details
Name: | us-gaap_DerivativeAssetAfterOffsetSubjectToMasterNettingArrangement
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of the assets less the liabilities of a derivative or group of derivatives. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-10 + Details
Name: | us-gaap_DerivativeFairValueOfDerivativeNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value, after effect of master netting arrangement, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and contract can be net settled by means outside contract or delivery of asset. Includes derivative subject to master netting arrangement not elected or qualified to offset. Excludes derivative not subject to master netting arrangement or similar agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483466/210-20-50-3 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 22 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483444/210-20-55-22 + Details
Name: | us-gaap_DerivativeLiabilityAfterOffsetSubjectToMasterNettingArrangement
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as noncurrent. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482736/825-10-45-1A + Details
Name: | us-gaap_EquitySecuritiesFVNINoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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 Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 100 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-100 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-3 + Details
Name: | us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
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 Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 103 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-103 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(2)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of firm holdings in corporate fixed income securities. Includes pledged and unpledged holdings. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 940 -SubTopic 320 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479035/940-320-45-2 + Details
Name: | us-gaap_FinancialInstrumentsOwnedCorporateDebtAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value as of the balance sheet date of firm holdings in physical commodity contracts (for example, agricultural products, metals and energy). Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings. + References No definition available. + Details
Name: | us-gaap_FinancialInstrumentsOwnedPhysicalCommoditiesAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The fair value as of the balance sheet date of firm holdings in debt obligations issued by the US government including short-term Treasury bills, medium-term Treasury notes, and long-term Treasury bonds, as well as debt issued by agencies. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 940 -SubTopic 320 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479035/940-320-45-2 + Details
Name: | us-gaap_FinancialInstrumentsOwnedUSGovernmentAndAgencyObligationsAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of liability contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward (delivery or nondelivery) contracts, and swaps entered into. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets. + References No definition available. + Details
Name: | us-gaap_InterestRateDerivativeAssetsAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities. + References No definition available. + Details
Name: | us-gaap_InterestRateDerivativeLiabilitiesAtFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2E -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_InvestmentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=tve_CommodityContractUnderFHPMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |