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v3.21.2

Summary of Significant Accounting Policies Revenues (Details) | Jun. 30, 2021 Units
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Accounting Policies [Abstract] |
Number of customers with billing dates before month end | 5

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- Definition Number of customers with billing dates before month end + References No definition available. + Details
Name: | tve_NumberOfCustomersWithBillingDatesBeforeMonthEnd
Namespace Prefix: | tve_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration