Income Taxes Income Taxes (Summary of Interest on Income Taxes Expense Related to Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 7.0	$ 8.0	$ 9.0
Entergy Arkansas [Member]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0.2	0.2	0.0
Entergy Louisiana [Member]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	3.8	5.7	(0.9)
Entergy Mississippi [Member]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0.2	0.2	0.4
Entergy New Orleans [Member]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0.6	0.6	(0.3)
Entergy Texas [Member]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0.5	(0.8)	0.7
System Energy [Member]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 4.7	$ 4.8	$ 5.2