Summary of Significant Accounting Policies General and Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013 variable_interest_entities People	Sep. 30, 2012
General and Basis of Presentation
Population of TVA's service area	9,000,000
Number of variable interest entities	2
Period of time for customers to fulfill payment arrangements	90 days
Allowance for uncollectible accounts, accounts receivable	$ 4	$ 7
Loans and other long-term receivables, net	79	76
Loans and other long-term receivables, allowance	11	12
Possible amount of future payments	250
Estimated future payments attributable to BLEU fuel currently in use	$ 34

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 8, 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Section 50

-Paragraph 2

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 210

-Section S99

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-Subparagraph (SX 210.9-03.7(d))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Paragraph 8

-Subparagraph a(ii)

-Chapter V

-Subsection I

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-Name Regulation S-X (SX)

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-Section 03

-Paragraph 7

-Subparagraph d

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

+ Details