XML 83 R50.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Debt and Other Obligations Debt Securities Activity (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Dec. 31, 2017 | Mar. 31, 2018 | Mar. 31, 2017
Debt Instrument |  |  |  |  |
Issues of power bonds |  |  | $ 998 |  | $ 999
Redemptions/maturities of power bonds |  |  | 700 | [1] | 528
Total redemptions/maturities of debt | [1] |  | 747 |  |
Repayments of Notes Payable |  |  | 29 |  | 26
Repayments of debt of variable interest entities |  |  | $ 18 |  | $ 17
2018 Series A |  |  |  |  |
Debt Instrument |  |  |  |  |
Percent of par value |  |  | 100.00% |  |
electronotes |  |  |  |  |
Debt Instrument |  |  |  |  |
Redemptions/maturities of power bonds |  | $ 47 |  |  |
Interest rate |  | 4.10% | 3.50% |  |
2009 Series B |  |  |  |  |
Debt Instrument |  |  |  |  |
Redemptions/maturities of power bonds |  | $ 1 |  |  |
Interest rate |  | 3.77% |  |  |
Total |  |  |  |  |
Debt Instrument |  |  |  |  |
Percent of par value |  |  | 100.00% |  |
Notes payable |  |  |  |  |
Debt Instrument |  |  |  |  |
Interest rate |  |  | 0.86% |  |
Repayments of Notes Payable |  |  | $ 29 |  |
1997 Series E |  |  |  |  |
Debt Instrument |  |  |  |  |
Redemptions/maturities of power bonds |  | $ 650 | 2 |  |
Interest rate |  | 6.25% |  |  |
Debt of variable interest entities [Member] |  |  |  |  |
Debt Instrument |  |  |  |  |
Repayments of debt of variable interest entities |  |  | $ 18 |  |
Other Debt instrument, Interest Rate, Effective Percentage |  |  | 4.31% |  |
2018 Series A |  |  |  |  |
Debt Instrument |  |  |  |  |
Issues of power bonds |  |  | $ 1,000 |  |
Interest rate |  |  | 2.25% |  |
Discount on debt issues |  |  | $ (2) |  |
Total |  |  |  |  |
Debt Instrument |  |  |  |  |
Issues of power bonds |  |  | $ 998 |  |
[1] | All redemptions were at 100 percent of par.

X
- Definition Effective interest rate for the funds borrowed under the other debt agreements considering interest compounding and original issue discount or premium. + References No definition available. + Details
Name: | tve_OtherDebtinstrumentInterestRateEffectivePercentage
Namespace Prefix: | tve_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- 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

X
- Definition Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: 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 + Details
Name: | us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
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 No definition available. + Details
Name: | us-gaap_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- 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

X
- 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 -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585 + Details
Name: | us-gaap_ProceedsFromIssuanceOfUnsecuredDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of cash inflow (outflow) for debt classified as other. + References No definition available. + Details
Name: | us-gaap_ProceedsFromRepaymentsOfOtherDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The cash outflow for a borrowing supported by a written promise to pay an obligation. + 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=98514028&loc=d3e3291-108585 + Details
Name: | us-gaap_RepaymentsOfNotesPayable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of cash outflow for the payment of debt classified as other, maturing after one year or the operating cycle, if longer. + 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=98514028&loc=d3e3291-108585 + Details
Name: | us-gaap_RepaymentsOfOtherLongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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 -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585 + Details
Name: | us-gaap_RepaymentsOfUnsecuredDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | tve_RedemptionsAndMaturitiesAxis=tve_A2018SeriesAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | tve_RedemptionsAndMaturitiesAxis=tve_ElectronotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | tve_RedemptionsAndMaturitiesAxis=tve_A2009SeriesBMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | tve_RedemptionsAndMaturitiesAxis=tve_TotalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | tve_RedemptionsAndMaturitiesAxis=tve_NotesPayableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | tve_RedemptionsAndMaturitiesAxis=tve_A1997SeriesEMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | tve_RedemptionsAndMaturitiesAxis=tve_DebtOfVariableInterestEntitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | tve_DebtissuesAxis=tve_A2018SeriesAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | tve_DebtissuesAxis=tve_TotalMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |