Risk Management Activities and Derivative Transactions Risk Management Activities and Derivative Transactions - Currency Swaps Outstanding (Details) (GBP £) In Millions, unless otherwise specified	Sep. 30, 2012 Bond_issues	Apr. 15, 2012
Derivative
Number of British pound sterling denominated bond transactions	3
Overall effective cost to TVA		8.25%
1999 Currency Swap Contract
Derivative
Effective date of currency swap contract	1999
Associated TVA bond issues currency exposure	200
Expiration date of swap	2021
Overall effective cost to TVA	5.81%
2001 Currency Swap Contract
Derivative
Effective date of currency swap contract	2001
Associated TVA bond issues currency exposure	250
Expiration date of swap	2032
Overall effective cost to TVA	6.59%
2003 Currency Swap Contract
Derivative
Effective date of currency swap contract	2003
Associated TVA bond issues currency exposure	150
Expiration date of swap	2043
Overall effective cost to TVA	4.96%