Leaseback obligation settled as a result of acquisition

No definition available.

Name:	tve_Leasebackobligationsettledasaresultofacquisition
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percent of par value that debt was issued/redeemed for.

+ References

No definition available.

+ Details

Name:	tve_PercentOfParValue
Namespace Prefix:	tve_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Amount, after accumulated amortization, of debt discount (premium).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28567-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

+ Details

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

- Definition

The amount of debt that an Entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

Name:	us-gaap_NoncashOrPartNoncashAcquisitionDebtAssumed1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

+ Details

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

- Definition

Amount of cash inflow (outflow) for debt classified as other.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

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

- Definition

Amount of cash outflow for the payment of debt classified as other.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3291-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

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

- Definition

Amount of cash outflow for the payment of debt classified as other, maturing after one year or the operating cycle, if longer.

+ References

+ Details

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

- Definition

The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3291-108585

+ Details

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

- Details

Name:	tve_RedemptionsAndMaturitiesAxis=tve_DebtOfVariableInterestEntitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_RedemptionsAndMaturitiesAxis=us-gaap_NotesPayableOtherPayablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_RedemptionsAndMaturitiesAxis=tve_ElectronotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_RedemptionsAndMaturitiesAxis=tve_A1998SeriesDMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_RedemptionsAndMaturitiesAxis=tve_A1999SeriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_RedemptionsAndMaturitiesAxis=tve_A2005SeriesBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_RedemptionsAndMaturitiesAxis=tve_A2009SeriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_RedemptionsAndMaturitiesAxis=tve_A2009SeriesBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_RedemptionsAndMaturitiesAxis=tve_TotalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_DebtissuesAxis=tve_A2015SeriesADomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	tve_DebtissuesAxis=tve_TotalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=tve_SpecialpurposeentityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=tve_TotalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt and Other Obligations Debt and Other Obligations - Debt Securities Activity (Details) - USD ($)	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Jul. 20, 2016
Debt Instrument
Issues of power bonds	$ 0	$ 973,000,000	$ 989,000,000
Discount on debt issues	0	(27,000,000)
Acquisition of notes payable		78,000,000
Redemptions/Maturities of variable interest entities	33,000,000	32,000,000	30,000,000
Redemptions/Maturities of power bonds	76,000,000	1,180,000,000	$ 365,000,000
Leaseback obligation settled as a result of acquisition				$ 70,000,000
Debt of variable interest entities
Debt Instrument
Redemptions/Maturities of variable interest entities	33,000,000	32,000,000
Notes Payable
Debt Instrument
Redemptions/Maturities of notes payable	3,000,000	0
Electronotes
Debt Instrument
Redemptions/Maturities of power bonds	47,000,000	62,000,000
1998 Series D
Debt Instrument
Redemptions/Maturities of power bonds	0	50,000,000
1999 Series A
Debt Instrument
Redemptions/Maturities of power bonds	0	38,000,000
2005 Series B
Debt Instrument
Redemptions/Maturities of power bonds	0	1,000,000,000
2009 Series A
Debt Instrument
Redemptions/Maturities of power bonds	2,000,000	3,000,000
2009 Series B
Debt Instrument
Redemptions/Maturities of power bonds	27,000,000	27,000,000
Total
Debt Instrument
Total	$ 112,000,000	1,212,000,000
Percent of par value	100.00%
2015 Series A
Debt Instrument
Issues of power bonds	$ 0	1,000,000,000
Percent of par value	97.31%
Total
Debt Instrument
Total	$ 0	973,000,000
Notes payable
Debt Instrument
Acquisition of notes payable	78,000,000	0
Total
Debt Instrument
Acquisition of notes payable	$ 78,000,000	$ 0