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Risk Management Activities and Derivative Transactions Currency Swaps Outstanding (Details) $ in Millions | 6 Months Ended
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Mar. 31, 2018 USD ($) Bond_issues
Derivative |
Number of British pound sterling denominated bond transactions | 3
Number of currency swaps outstanding | 3
Associated TVA bond issues currency exposure | $ | $ 600
Minimum |
Derivative |
Expiration date range of swaps | 2021
Maximum |
Derivative |
Expiration date range of swaps | 2043

X
- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References No definition available. + Details
Name: | tve_AssociatedBondIssuesCurrencyExposure
Namespace Prefix: | tve_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Expiration Date of Swap + References No definition available. + Details
Name: | tve_ExpirationDateofSwap
Namespace Prefix: | tve_
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Balance Type: | na
Period Type: | duration

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- Definition Number of British pound streling denominated bond transactions + References No definition available. + Details
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Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
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- Definition Number of foreign currency exchange rate derivatives held by the entity at the reporting date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959 + Details
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