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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
Dec. 31, 2013
Customers
Sep. 30, 2013
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   $ 175
Estimated future payments attributable to blended low-enriched uranium fuel currently in use   106
Maximum original maturity   3 months
Subsequent period after a nuclear refueling outage when the benefits of the costs are realized - minimum   18 months
Subsequent period after a nuclear refueling outage when the benefits of the costs are realized - maximum   24 months
Recorded cost for emission allowances granted by the Environmental Protection Agency   0
BLEU fuel obligation   $ 6