Leases (Details) - USD ($) $ in Millions	Jun. 30, 2022	Sep. 30, 2021
Amounts Recognized on TVA's Consolidated Balance Sheet [Line Items]
Finance lease, asset	$ 645	$ 692
Finance Lease, Liability, Current	0	25
Operating Lease, Liability, Noncurrent	111	122
Finance Lease, Liability, Noncurrent	$ 648	$ 687

[Line Items] for Amounts Recognized on TVA's Consolidated Balance Sheet [Table]

No definition available.

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

- Definition

Finance lease, asset

+ References

No definition available.

+ Details

Name:	tve_Financeleaseasset
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Present value of lessee's discounted obligation for lease payments from finance lease, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123391704&loc=SL77918627-209977

+ Details

Name:	us-gaap_FinanceLeaseLiabilityCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Present value of lessee's discounted obligation for lease payments from finance lease, classified as noncurrent.

+ References

+ Details

Name:	us-gaap_FinanceLeaseLiabilityNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.

+ References

+ Details

Name:	us-gaap_OperatingLeaseLiabilityNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant