Prepayment period

No definition available.

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Period Type:	duration

- Definition

Amount of previously reported deferred or unearned revenue that was recognized as revenue during the period. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 13.A.4(a).Q1)

-URI http://asc.fasb.org/extlink&oid=27012821&loc=d3e214044-122780

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 13

-Section A

+ Details

Name:	us-gaap_DeferredRevenueRevenueRecognized
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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_EntityWideInformationRevenueFromExternalCustomerLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The increase (decrease) during the reporting period, excluding the portion taken into income, in the liability reflecting revenue yet to be earned for which cash or other forms of consideration was received or recorded as a receivable.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

+ Details

Name:	us-gaap_IncreaseDecreaseInDeferredRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of consideration recognized during the period for the milestone or milestones.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 28

-Section 50

-Paragraph 2

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=51671726&loc=SL6892177-166501

+ Details

Name:	us-gaap_RevenueRecognitionMilestoneMethodRevenueRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Aggregate cash discounts given by the entity for services rendered to customers for early payments of accounts due. For example, selling terms of "2/10, net 30" entitle a customer to a 2% discount for prompt payment within 10 days, otherwise full payment is expected in 30 days. Discounts are a deduction from gross revenue in arriving at net revenue.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1(a))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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

- Details

Name:	us-gaap_DeferredRevenueArrangementTypeAxis=tve_MlgwMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_DeferredRevenueArrangementTypeAxis=tve_TotalMember
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Period Type:

Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Energy Prepayment Obligations and Discounts on Sales (Details) - USD ($) $ in Millions	12 Months Ended				132 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2004	Sep. 30, 2015
Energy Prepayment Obligations and Discounts on Sales
MLGW prepayment				$ 1,500
MLGW prepayment period				180 months
MLGW
Energy Prepayment Obligations and Discounts on Sales
Deferred revenue expected recognition each year	$ 100
Deferred revenue, revenue recognized	100	$ 100	$ 100		$ 1,200
Total
Energy Prepayment Obligations and Discounts on Sales
Discounts reducing electricity sales	$ 46	$ 46	$ 46