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Summary of Significant Accounting Policies Summary of Significant Accounting Policies - General (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014 Customers People
Population of Service Area
Number of customers for whom unbilled revenues are estimated	6
Population of TVA's service area (number of people)	9,000,000
Possible amount of future payments to the Department of Energy under the blended low-enriched uranium program	$ 160
Estimated future payments attributable to blended low-enriched uranium fuel currently in use	101
Maximum original maturity	3 months
Recorded cost for emission allowances granted by the Environmental Protection Agency	0
BLEU fuel obligation	$ 16

X

- Definition

The liability established for payments due that are attributable to blended low-enriched uranium fuel that has been used.

+ References

No definition available.

+ Details

Name:	tve_BLEUfuelobligation
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Maximum original maturity

+ References

No definition available.

+ Details

Name:	tve_Maximumoriginalmaturity
Namespace Prefix:	tve_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The number of customers for whom unbilled revenues are estimated.

+ References

No definition available.

+ Details

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

X

- Definition

Payments attributable to blended low-enriched uranium fuel program

+ References

No definition available.

+ Details

Name:	tve_PaymentsattributabletoBLEUfuelprogram
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

The population of the company's service area.

+ References

No definition available.

+ Details

Name:	tve_PopulationOfServiceArea
Namespace Prefix:	tve_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Details

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

X

- Definition

Recorded cost for emission allowances granted by the Environmental Protection Agency

+ References

No definition available.

+ Details

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

X

- Definition

Total of past and projected future payments that TVA may make to the DOE over the duration of the BLEU fuel program, from inception to termination. It includes the amounts paid out, plus an estimated amount related to possible future payments that may be payable to the DOE until the time that the BLEU fuel program ceases to be in effect.

+ References

No definition available.

+ Details

Name:	tve_TotalpossibleamountofBLEUpayments
Namespace Prefix:	tve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant