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Fair Value Measurements Fair Value Measurements Using Significant Unobservable Inputs (Details) (USD $) | 3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 31, 2015 Contracts | Mar. 31, 2015 Contracts | Mar. 31, 2014 | Mar. 31, 2014 | Sep. 30, 2014 tons-per-year | Dec. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2013
ASSETS |  |  |  |  |  |  |  |  |  |
Commodity contract derivatives | $ 5,000,000 us-gaap_FinancialInstrumentsOwnedPhysicalCommoditiesAtFairValue | $ 5,000,000 us-gaap_FinancialInstrumentsOwnedPhysicalCommoditiesAtFairValue |  |  |  | $ 1,000,000 us-gaap_FinancialInstrumentsOwnedPhysicalCommoditiesAtFairValue |  |  |  |
Liabilities |  |  |  |  |  |  |  |  |  |
Commodity contract derivatives | 154,000,000 tve_Commoditycontractderivativeliabilitiesfairvaluedisclosure | 154,000,000 tve_Commoditycontractderivativeliabilitiesfairvaluedisclosure |  |  |  | 97,000,000 tve_Commoditycontractderivativeliabilitiesfairvaluedisclosure |  |  |  |
Number of contracts | 1 tve_NumberOfContracts | 1 tve_NumberOfContracts |  |  |  | 2 tve_NumberOfContracts |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |  |  |  |  |
Amount of gain (loss) recognized in income | 0 us-gaap_DerivativeGainLossOnDerivativeNet | 0 us-gaap_DerivativeGainLossOnDerivativeNet |  |  |  |  |  |  |  |
Private Partnerships |  |  |  |  |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |  |  |  |  |
Balance | 223,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 223,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  | 180,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 180,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 214,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  | 220,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 169,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 159,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember
Purchases | 4,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityPurchases / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 10,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityPurchases / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  | 6,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityPurchases / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 14,000,000 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityPurchases / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  |  |  |  |
Issuances | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityIssues / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityIssues / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityIssues / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityIssues / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  |  |  |  |
Sales | (3,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySales / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | (7,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySales / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  | (2,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySales / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | (5,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySales / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  |  |  |  |
Settlements | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySettlements / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySettlements / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySettlements / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySettlements / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  |  |  |  |
Net unrealized gains (losses) deferred as regulatory assets and liabilities | 2,000,000 tve_FairValueAssetsOrLiabilitiesMeasuredOnRecurringBasisGainLossDeferredAsRegulatoryAssetsOrLiabilities / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 6,000,000 tve_FairValueAssetsOrLiabilitiesMeasuredOnRecurringBasisGainLossDeferredAsRegulatoryAssetsOrLiabilities / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  | 7,000,000 tve_FairValueAssetsOrLiabilitiesMeasuredOnRecurringBasisGainLossDeferredAsRegulatoryAssetsOrLiabilities / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember | 12,000,000 tve_FairValueAssetsOrLiabilitiesMeasuredOnRecurringBasisGainLossDeferredAsRegulatoryAssetsOrLiabilities / tve_FairValueByClassAxis = us-gaap_PartnershipInterestMember |  |  |  |  |
Commodity Contract Derivatives |  |  |  |  |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |  |  |  |  |
Balance | (149,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | (149,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  | (131,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | (131,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | (96,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  | (133,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | (145,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | (140,000,000)tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue / tve_FairValueByClassAxis = us-gaap_CommodityContractMember
Purchases | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityPurchases / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityPurchases / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityPurchases / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityPurchases / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  |  |  |  |
Issuances | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityIssues / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityIssues / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityIssues / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityIssues / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  |  |  |  |
Sales | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySales / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySales / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySales / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySales / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  |  |  |  |
Settlements | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySettlements / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySettlements / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySettlements / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | 0 tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySettlements / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  |  |  |  |
Net unrealized gains (losses) deferred as regulatory assets and liabilities | (16,000,000)tve_FairValueAssetsOrLiabilitiesMeasuredOnRecurringBasisGainLossDeferredAsRegulatoryAssetsOrLiabilities / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | (53,000,000)tve_FairValueAssetsOrLiabilitiesMeasuredOnRecurringBasisGainLossDeferredAsRegulatoryAssetsOrLiabilities / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  | 14,000,000 tve_FairValueAssetsOrLiabilitiesMeasuredOnRecurringBasisGainLossDeferredAsRegulatoryAssetsOrLiabilities / tve_FairValueByClassAxis = us-gaap_CommodityContractMember | 9,000,000 tve_FairValueAssetsOrLiabilitiesMeasuredOnRecurringBasisGainLossDeferredAsRegulatoryAssetsOrLiabilities / tve_FairValueByClassAxis = us-gaap_CommodityContractMember |  |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |
ASSETS |  |  |  |  |  |  |  |  |  |
Fair value inputs, counterparty credit risk |  | 0.25%us-gaap_FairValueInputsCounterpartyCreditRisk / us-gaap_RangeAxis = us-gaap_MaximumMember | [1] |  |  | 5.00%us-gaap_FairValueInputsCounterpartyCreditRisk / us-gaap_RangeAxis = us-gaap_MaximumMember | [2] |  |  |
Fair value measurements tons per year | 1,000,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MaximumMember | 1,000,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  | 1,100,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |
Price per ton | 103.41 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MaximumMember | 103.41 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  | 67.07 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |
Liabilities |  |  |  |  |  |  |  |  |  |
Fair value measurements tons per year | 1,000,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MaximumMember | 1,000,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  | 1,100,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |
Price per ton | 103.41 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MaximumMember | 103.41 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  | 67.07 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |
Minimum |  |  |  |  |  |  |  |  |  |
ASSETS |  |  |  |  |  |  |  |  |  |
Fair value inputs, counterparty credit risk |  | 0.25%us-gaap_FairValueInputsCounterpartyCreditRisk / us-gaap_RangeAxis = us-gaap_MinimumMember | [1] |  |  | 2.00%us-gaap_FairValueInputsCounterpartyCreditRisk / us-gaap_RangeAxis = us-gaap_MinimumMember | [2] |  |  |
Fair value measurements tons per year | 800,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MinimumMember | 800,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  | 1,000,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  |
Price per ton | 10.74 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MinimumMember | 10.74 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  | 11.24 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  |
Liabilities |  |  |  |  |  |  |  |  |  |
Fair value measurements tons per year | 800,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MinimumMember | 800,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  | 1,000,000,000 tve_FairValueMeasurementsTonsPerYear / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  |
Price per ton | 10.74 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MinimumMember | 10.74 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  | 11.24 tve_PricePerTon / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  |
Fair Value, Inputs, Level 3 |  |  |  |  |  |  |  |  |  |
ASSETS |  |  |  |  |  |  |  |  |  |
Commodity contract derivatives | 5,000,000 us-gaap_FinancialInstrumentsOwnedPhysicalCommoditiesAtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | 5,000,000 us-gaap_FinancialInstrumentsOwnedPhysicalCommoditiesAtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |  |  |  | 1,000,000 us-gaap_FinancialInstrumentsOwnedPhysicalCommoditiesAtFairValue / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |  |  |  |
Liabilities |  |  |  |  |  |  |  |  |  |
Commodity contract derivatives | $ 154,000,000 tve_Commoditycontractderivativeliabilitiesfairvaluedisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member | $ 154,000,000 tve_Commoditycontractderivativeliabilitiesfairvaluedisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |  |  |  | $ 97,000,000 tve_Commoditycontractderivativeliabilitiesfairvaluedisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member |  |  |  |
[1] | Applies to only one contract.
[2] | Applies to two contracts.

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
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Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition This item represents the amount of the total realized and unrealized gains or losses for the period which are deferred as regulatory assets and liabilities; the fair value of which assets or liabilities was or is measured on a recurring basis using significant unobservable inputs (Level 3). + References No definition available. + Details
Name: | tve_FairValueAssetsOrLiabilitiesMeasuredOnRecurringBasisGainLossDeferredAsRegulatoryAssetsOrLiabilities
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition The fair value measurement of tons per year used to determine fair value + References No definition available. + Details
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Namespace Prefix: | tve_
Data Type: | num:weightItemType
Balance Type: | na
Period Type: | instant

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- Definition Issues that have taken place during the period in relation to assets or liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy. + References No definition available. + Details
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Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Purchases that have taken place during the period in relation to assets or liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy. + References No definition available. + Details
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Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Sales that have taken place during the period in relation to assets or liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy. + References No definition available. + Details
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Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Settlements that have taken place during the period in relation to assets or liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy. + References No definition available. + Details
Name: | tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilitySettlements
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition This element represents an asset or liability measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances. + References No definition available. + Details
Name: | tve_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetOrLiabilityValue
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition The number of contracts the range applies to. + References No definition available. + Details
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Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition The price per ton used for the determination of fair value. + References No definition available. + Details
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Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | us-gaap_AssetsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Details
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Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Risk that one party to the contract will default expressed as a percentage, used as an input to measure fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- 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
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
Name: | tve_FairValueByClassAxis=us-gaap_PartnershipInterestMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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