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v3.19.3

Plant Closures (Details) $ in Millions | 12 Months Ended
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Sep. 30, 2019 USD ($)
Property, Plant and Equipment [Abstract] |
Write-offs related to retirement of plants | $ 151
Write-offs materials and supplies | 19
Accelerated depreciation | $ 566

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- Definition Accelerated depreciation + 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 Write-offs materials and supplies + 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 Write-offs related to retirement of plants + 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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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
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