Banking Counterparties Credit Rating

No definition available.

Name:	tve_BankingCounterpartiesCreditRating
Namespace Prefix:	tve_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Natural Gas Banking Counterparties Credit Rating

+ References

No definition available.

+ Details

Name:	tve_NaturalGasBankingCounterpartiesCreditRating
Namespace Prefix:	tve_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of customers that represent the percent of sales

+ References

No definition available.

+ Details

Name:	tve_Numberofcustomersthatrepresentthepercentofsales
Namespace Prefix:	tve_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

This concept explains the total percentage of operating revenue provided by the two largest customers.

+ References

No definition available.

+ Details

Name:	tve_TwoLargestCustomerPercentageOfTotalOperatingRevenue
Namespace Prefix:	tve_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=124098289&loc=d3e6676-107765

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 9
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4531-111522

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(a)(1))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_AccountsReceivableGrossCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, not subject to a master netting arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=99393222&loc=SL20226052-175313

+ Details

Name:	us-gaap_DerivativeAssetNotSubjectToMasterNettingArrangement
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysA1RatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysCaa1RatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=tve_CreditOfCustomersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Risk Management Activities and Derivative Transactions Counterparty Credit Risk (Details) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2023 USD ($) Customers	Sep. 30, 2022 USD ($)
Derivative
Accounts Receivable, before Allowance for Credit Loss, Current \| $	$ 1,420	$ 1,420	$ 1,899
Total derivatives not subject to master netting or similar arrangement \| $	$ 25	$ 25	$ 152
Two Largest Customer Percentage of Total Operating Revenue	1600.00%
Moody's, A1 Rating [Member]
Derivative
Banking Counterparties Credit Rating		A2
Natural Gas Banking Counterparties Credit Rating		A1
Moody's, Caa1 Rating [Member]
Derivative
Natural Gas Banking Counterparties Credit Rating		B1
Credit of Customers
Derivative
Number of customers that represent the percent of sales \| Customers		2
Number of customers that represent the percent of sales \| Customers		2