XML 86 R60.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Fair Value Measurements Fair Value Measurements - Investments (Details) $ in Millions | 3 Months Ended
--- | ---
Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Investment Gains (Losses) |  |
Investment fund securities classified as trading and measured at fair value | $ 2,300 |
Balance in NDT | 1,700 |
Balance in ART | $ 525 |
Period of time where the investor contributes capital to an investment in a private partnership - minimum | 3 years |
Period of time where the investor contributes capital to an investment in a private partnership - maximum | 4 years |
Minimum investment period | 10 years |
Number of readily available quoted exchange prices for the investments | 0 |
NDT |  |
Investment Gains (Losses) |  |
Unrealized gains (losses) on investments | $ (7) | $ 39
ART |  |
Investment Gains (Losses) |  |
Unrealized gains (losses) on investments | 3 | $ 12
Equity Funds |  |
Investment Gains (Losses) |  |
NDT unfunded commitments related to private equity and real estate | 60 |
Real Estate Funds |  |
Investment Gains (Losses) |  |
NDT unfunded commitments related to private equity and real estate | $ 5 |

X
- Definition Minimum investment period of private partnership investments. + References No definition available. + Details
Name: | tve_Minimuminvestmentperiod
Namespace Prefix: | tve_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning nuclear facilities. + References No definition available. + Details
Name: | tve_NuclearDecommissioningFundInvestmentsFairValue
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number of readily available quoted exchange prices for the investments + References No definition available. + Details
Name: | tve_NumberOfReadilyAvailableQuotedExchangePricesForInvestments
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Period of time where the investor contributes capital to an investment in a private partnership - maximum + References No definition available. + Details
Name: | tve_Periodoftimewheretheinvestorcontributescapitaltoaninvestmentinaprivatepartnershipmaximum
Namespace Prefix: | tve_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period of time where the investor contributes capital to an investment in a private partnership - minimum + References No definition available. + Details
Name: | tve_Periodoftimewheretheinvestorcontributescapitaltoaninvestmentinaprivatepartnershipminimum
Namespace Prefix: | tve_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value portion of arrangements with third parties, including, but not limited to, operating lease arrangement and arrangement in which the entity has agreed to expend funds to procure goods or services, or has agreed to commit resources to supply goods or services. + 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(25)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_CommitmentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The fair value of investments held in a trust fund to pay for the costs of decontaminating and decommissioning facilities, whether such amount is presented as a separate caption or as a parenthetical disclosure on the balance sheet. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
Name: | us-gaap_DecommissioningTrustAssetsAmount
Namespace Prefix: | us-gaap_
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_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesReportableDataLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26626-111562 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26610-111562 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 + Details
Name: | us-gaap_TradingSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period. + 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 (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 + Details
Name: | us-gaap_UnrealizedGainLossOnInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | invest_InvestmentAxis=tve_NdtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | invest_InvestmentAxis=tve_ArtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_EquityFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_RealEstateFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |