Leaseback Obligations Leaseback Obligations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2003 Units	Sep. 30, 2012 Basis_points Agencies	Sep. 30, 2011
Leaseback Obligations
Proceeds prior to 2004	$ 945
Number of new peaking combustion turbine units in leaseback transactions	24
Proceeds in 2003	389
CT/QTE outstanding leaseback obligation		825	885
SSSL undivided interest		90.00%
Southaven leaseback obligation		$ 378	$ 397
Basis points if TVA's rating is AAA		62.5
Basis points if TVA's rating is AA plus		87.5
Number of credit rating agencies		1