Income Taxes (Summary Of Unrecognized Benefits That Would Affect Effective Income Tax Rate) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Unrecognized tax benefits that would impact effective income tax rate	$ 955.0	$ 516.0	$ 176.0
Entergy Arkansas [Member]
Unrecognized tax benefits that would impact effective income tax rate	4.5	2.6	0.6
Entergy Louisiana [Member]
Unrecognized tax benefits that would impact effective income tax rate	692.7	267.3	131.9
Entergy Mississippi [Member]
Unrecognized tax benefits that would impact effective income tax rate	8.1	3.9	3.9
Entergy New Orleans [Member]
Unrecognized tax benefits that would impact effective income tax rate	50.7	50.7	0.0
Entergy Texas [Member]
Unrecognized tax benefits that would impact effective income tax rate	5.2	10.5	10.1
System Energy [Member]
Unrecognized tax benefits that would impact effective income tax rate	$ 0.7	$ 3.7	$ 3.3