Income Taxes (Summary Of Unrecognized Benefits That Would Affect Effective Income Tax Rate) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Unrecognized tax benefits that would impact effective income tax rate	$ 1,240.0	$ 63.5	$ 955.0	$ 516.0
Entergy Arkansas [Member]
Unrecognized tax benefits that would impact effective income tax rate	3.6		4.5	2.6
Entergy Louisiana [Member]
Unrecognized tax benefits that would impact effective income tax rate	473.3	$ 61.6	692.7	267.3
Entergy Mississippi [Member]
Unrecognized tax benefits that would impact effective income tax rate	0.0		8.1	3.9
Entergy New Orleans [Member]
Unrecognized tax benefits that would impact effective income tax rate	33.6		50.7	50.7
Entergy Texas [Member]
Unrecognized tax benefits that would impact effective income tax rate	7.0		5.2	10.5
System Energy [Member]
Unrecognized tax benefits that would impact effective income tax rate	$ 0.0		$ 0.7	$ 3.7