Leases (Rent Expenses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Rent Expense	$ 53.1	$ 44.4	$ 63.9
Entergy Arkansas [Member]
Rent Expense	7.5	8.0	13.6
Entergy Louisiana [Member]
Rent Expense	23.0	17.8	21.8
Entergy Mississippi [Member]
Rent Expense	5.6	4.0	5.4
Entergy New Orleans [Member]
Rent Expense	2.5	0.9	1.6
Entergy Texas [Member]
Rent Expense	3.4	2.8	4.0
System Energy [Member]
Rent Expense	$ 2.2	$ 1.6	$ 2.9