XML 162 R121.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Commitments and Contingencies Commitments and Contingencies - Legal Proceedings (Details) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2018 USD ($) People Units megawatts Groups Agreements | Sep. 30, 2017 USD ($)
Legal Proceedings |  |
Possible additional future costs for compliance with CCR requirements | $ 1,178 |
Amount spent under environmental agreements | 276 |
Contribution related to TVARS case | 15 | $ 20
Possible additional future costs for compliance with Clean Water requirements. | 466 |
Amount to Pay Consent Decree | 0 |
General |  |
Legal Proceedings |  |
Legal loss contingency accrual | $ 18 |
Environmental Agreements |  |
Legal Proceedings |  |
Number of similar environmental agreements entered into | Agreements | 2 |
Number of environmental agreements entered into with the EPA | Agreements | 1 |
Number of environmental agreements entered into with environmental advocacy groups | Groups | 3 |
Number of units to be idled | Units | 18 |
Megawatts option 1 | megawatts | 2,200 |
Megawatts option 2 | 3,500 |
Amount to be invested in certain environmental projects | $ 290 |
Amount to be provided to fund environmental projects | 60 |
Amount to pay civil penalties | $ 10 |
Case Involving Tennessee Valley Authority Retirement System |  |
Legal Proceedings |  |
Number of participants that filed suit | People | 8 |
Contribution related to TVARS case | $ 1,000 |
Other long-term liabilities | General |  |
Legal Proceedings |  |
Legal loss contingency accrual | 11 |
Accounts payable and accrued liabilities | General |  |
Legal Proceedings |  |
Legal loss contingency accrual | $ 7 |

X
- Definition Amount to be invested in certain environmental projects + References No definition available. + Details
Name: | tve_AmountToBeInvestedInCertainEnvironmentalProjects
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount to be provided to fund environmental projects in Alabama, Kentucky, North Carolina, and Tennessee + References No definition available. + Details
Name: | tve_AmountToBeProvidedToFundEnvironmentalProjects
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount to pay civil penalties + References No definition available. + Details
Name: | tve_AmountToPayCivilPenalties
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount spent under environmental agreements + References No definition available. + Details
Name: | tve_Amountspentunderenvironmentalagreements
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount to Pay Consent Decree + References No definition available. + Details
Name: | tve_AmounttoPayConsentDecree
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Megawatts of summer net capability + References No definition available. + Details
Name: | tve_Megawatts
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Megawatts option 2 + References No definition available. + Details
Name: | tve_MegawattsOption2
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of environmental agreements entered into with the EPA + References No definition available. + Details
Name: | tve_NumberOfEnvironmentalAgreementsEnteredIntoWithEpa
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of participants that filed suit. + References No definition available. + Details
Name: | tve_NumberOfParticipantsThatFiledSuit
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of similar environmental agreements entered into + References No definition available. + Details
Name: | tve_NumberOfSimilarEnvironmentalAgreementsEnteredInto
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of units to be idled. + References No definition available. + Details
Name: | tve_NumberOfUnitsToBeIdled
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number environmental advocacy groups with which there is an environmental agreement. + References No definition available. + Details
Name: | tve_Numberenvironmentaladvocacygroupswithwhichthereisanenvironmentalagreement.
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The possible additional future costs for compliance with CCR requirements + References No definition available. + Details
Name: | tve_PossibleadditionalfuturecostsforcompliancewithCCRrequirements
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The possible additional future costs for compliance with Clean Water requirements. + References No definition available. + Details
Name: | tve_PossibleadditionalfuturecostsforcompliancewithCleanWaterrequirements.
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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_LossContingenciesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of loss contingency liability. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 + Details
Name: | us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of cash outflow for pension and other postretirement benefits. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3536-108585 + Details
Name: | us-gaap_PensionAndOtherPostretirementBenefitContributions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | srt_LitigationCaseAxis=tve_GeneralMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_LitigationCaseAxis=tve_EnvironmentalAgreementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_LitigationCaseAxis=tve_CaseInvolvingTennesseeValleyAuthorityRetirementSystemMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_OtherNoncurrentLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_AccountsPayableAndAccruedLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |