Income Taxes (Summary Of Unrecognized Benefits That Would Affect Effective Income Tax Rate) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Unrecognized tax benefits that would impact effective income tax rate	$ 203.0	$ 521.0	$ 605.0
Entergy Arkansas [Member]
Unrecognized tax benefits that would impact effective income tax rate	0.6		0.2
Entergy Gulf States Louisiana [Member]
Unrecognized tax benefits that would impact effective income tax rate	44.0	107.9	129.6
Entergy Louisiana [Member]
Unrecognized tax benefits that would impact effective income tax rate	92.4	281.3	286.7
Entergy Mississippi [Member]
Unrecognized tax benefits that would impact effective income tax rate	3.9	3.8	5.3
Entergy Texas [Member]
Unrecognized tax benefits that would impact effective income tax rate	8.6	7.3	6.0
System Energy [Member]
Unrecognized tax benefits that would impact effective income tax rate	$ 3.5		$ 12.1