Asset Retirement Obligations (Difference Between Estimated Incurred Removal Costs And Estimated Removal Costs Recovered In Rates) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016
Entergy Arkansas [Member]
Asset Retirement Obligations [Line Items]
Regulatory Assets	$ 176.9	$ 128.5
Entergy Louisiana [Member]
Asset Retirement Obligations [Line Items]
Regulatory Liabilities	(32.4)	(53.9)	$ (16.1)
Entergy Mississippi [Member]
Asset Retirement Obligations [Line Items]
Regulatory Assets	91.6	82.0
Entergy New Orleans [Member]
Asset Retirement Obligations [Line Items]
Regulatory Assets	44.8	40.1
Entergy Texas [Member]
Asset Retirement Obligations [Line Items]
Regulatory Assets	55.2	33.5
System Energy [Member]
Asset Retirement Obligations [Line Items]
Regulatory Assets	$ 67.9	$ 69.7