Income Taxes (Summary Of Accrued Interest And Penalties Related To Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accrued income tax interest and penalties	$ 38.0	$ 30.0	$ 27.0
Entergy Arkansas [Member]
Accrued income tax interest and penalties	1.6	1.4	1.3
Entergy Louisiana [Member]
Accrued income tax interest and penalties	14.1	8.4	9.3
Entergy Mississippi [Member]
Accrued income tax interest and penalties	1.0	0.8	0.4
Entergy New Orleans [Member]
Accrued income tax interest and penalties	2.1	1.5	1.8
Entergy Texas [Member]
Accrued income tax interest and penalties	0.4	1.2	1.2
System Energy [Member]
Accrued income tax interest and penalties	$ 8.5	$ 3.7	$ 0.7