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Debt and Other Obligations Debt and Other Obligations - Put and Call Options (Details) $ in Millions | 12 Months Ended
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Sep. 30, 2019 USD ($)
Debt Instrument |
Amount of redeemable bond issues outstanding | $ 357
Call price | 100.00%
Bond issues with survivor's option | 217
Amount of bonds redeemed | $ 217
PARRS 1998 Series D Bond |
Debt Instrument |
Amount of redeemable bond issues outstanding | $ 274
PARRS interest rate prior to rate reset | 6.75%
PARRS interest rate after rate reset | 3.55%
Amount of bonds redeemed | $ 301
PARRS 1999 Series A Bond |
Debt Instrument |
Amount of redeemable bond issues outstanding | $ 232
PARRS interest rate prior to rate reset | 6.50%
PARRS interest rate after rate reset | 3.36%
Amount of bonds redeemed | $ 293

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- Definition The amount of bonds redeemed. + References No definition available. + Details
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Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of redeemable bond issues outstanding + References No definition available. + Details
Name: | tve_AmountOfRedeemableBondIssuesOutstanding
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition The number of bond issues which include a "survivor's option" allowing for the right of redemption upon the death of a beneficial owner in certain specified circumstances. + References No definition available. + Details
Name: | tve_BondIssuesWithSurvivorsOption
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition Call price - low end of range. Shown as a percent of principal amount. + References No definition available. + Details
Name: | tve_CallPricePercent
Namespace Prefix: | tve_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition The PARRS interest rate after rate reset. + References No definition available. + Details
Name: | tve_ParrsInterestRateAfterRateReset
Namespace Prefix: | tve_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition The PARRS interest rate prior to rate reset. + References No definition available. + Details
Name: | tve_ParrsInterestRatePriorToRateReset
Namespace Prefix: | tve_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- 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
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Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |