Name:	tve_DefinedContributionPlanAutomaticEmployerContribution
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The amount per dollar that an employer matches employee contributions to a defined contribution plan.

No definition available.

Name:	tve_DefinedContributionPlanEmployerMatchingContributionRate
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Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

The maximum annual contribution that employees can make to the fixed and variable fund benefit. The fixed fund benefit is a benefit that earns a specified rate of interest on contributions made by employees. The variable fund is a benefit that invests employee contributions in the Spartan U.S. Equity Index Fund-Fidelity Advantage Class (Spartan).

No definition available.

Name:	tve_FixedAndVariableFundMaximumAnnualContribution
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The interest rate subtracted from the actuarial return and compared to six percent to credit balances in the fixed fund benefit after January 1, 2010. The lesser of the two interest rates is used to credit the fixed fund balances. The fixed fund benefit is a benefit that earns a specified rate of interest on employee contributions.

No definition available.

Name:	tve_FixedFundBalanceCreditPercentageSubtractedFromActuarialRateOfReturnAfterJanuary12010
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Data Type:	num:percentItemType
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Period Type:	duration

The interest rate compared to the actuarial return less 0.5 percent to credit balances in a fixed fund benefit after January 1, 2010. The lesser of the two interest rates is used to credit the fixed fund balances. The fixed fund benefit is a benefit that earns a specified rate of interest on employee contributions.

No definition available.

Name:	tve_FixedFundBalanceInterestCreditRateAfterJanuary12010
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The amount of interest credited to balances in the fixed fund benefit. The fixed fund benefit is a benefit that earns a specified rate of interest on employee contributions.

No definition available.

Name:	tve_FixedFundInterestCreditAmount
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The interest rate used to credit balances in the fixed fund benefit. The fixed fund benefit is a benefit that earns a specified rate of interest on employee contributions.

No definition available.

Name:	tve_FixedFundInterestCreditRate
Namespace Prefix:	tve_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The number of years for the phase-in period in which the impact of asset performance on pension expense is phased-in through a market-related value of asset calculation.

No definition available.

Name:	tve_MarketRelatedValuePhaseInPeriodNumberOfYears
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The maximum interest credit percentage for accounts of members of the Cash Balance Benefit.

No definition available.

Name:	tve_MaximumInterestCreditPercentageForCashBalanceBenefit
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The minimum interest credit percentage for accounts of memebers of the Cash Balance Benefit.

No definition available.

Name:	tve_MinimumInterestCreditPercentageForCashBalanceBenefit
Namespace Prefix:	tve_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The number of consecutive highest base pay years used to calculate the member's average monthly salary for those members participating in the Original Benefit Structure.

No definition available.

Name:	tve_NumberOfConsecutiveHighestBasePayYears
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The number of qualified defined benefit pension plans.

No definition available.

Name:	tve_NumberOfQualifiedDefinedBenefitPlans
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The number of qualified defined contribution pension plans.

No definition available.

Name:	tve_NumberOfQualifiedDefinedContributionPlans
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The number of unfunded post-retirement health care plans that provide for non-vested contributions toward the cost of certain retirees' medical coverage.

No definition available.

Name:	tve_NumberOfUnfundedPostRetirementHealthCarePlans
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number of defined benefit plan pension structures

No definition available.

Name:	tve_Numberofbenefitplanstructures
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The number of defined benefit plan investment funds.

No definition available.

Name:	tve_Numberofdefinedbenefitplaninvestmentfunds
Namespace Prefix:	tve_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The percentage added to the consumer price index for the interest credit to members' accounts of the Cash Balance Benefit

No definition available.

Name:	tve_PercentageAddedToConsumerPriceIndexForInterestCreditOfCashBalanceBenefit
Namespace Prefix:	tve_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The percentage of straight-time earnings that is used to credit the accounts of Cash Balance Benefit members.

No definition available.

Name:	tve_PercentageOfStraightTimeEarningsForCashBalanceBenefitCredit
Namespace Prefix:	tve_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The percentage of Cash Balance Benefit credit for specific calendar years.

No definition available.

Name:	tve_RateOfCashBalanceBenefitCreditForCalendarYear
Namespace Prefix:	tve_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

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.

No definition available.

Name:	us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The amount of the cost recognized during the period for defined contribution plans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Name:	tve_DefinedBenefitPlanStructureAxis=tve_OriginalBenefitStructureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	tve_DefinedBenefitPlanStructureAxis=tve_CashBalanceBenefitStructureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	tve_DefinedBenefitPlanStructureAxis=tve_DefinedContributionOnlyMemberDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
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