Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Fair value of debt securities by contractual maturities
Less than 1 year	$ 73.0	$ 77.0
1 year - 5 years	839.0	857.0
5 years - 10 years	755.0	704.0
10 years - 15 years	152.0	124.0
15 years - 20 years	63.0	50.0
20 years+	391.0	343.0
Total	2,273.0	2,155.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	5.4	1.8
1 year - 5 years	119.9	145.2
5 years - 10 years	163.5	138.5
10 years - 15 years	9.7	2.4
15 years - 20 years	1.1	2.0
20 years+	5.6	14.0
Total	305.2	303.9
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	18.9	27.1
1 year - 5 years	115.0	124.0
5 years - 10 years	117.1	114.3
10 years - 15 years	51.8	39.3
15 years - 20 years	30.9	26.5
20 years+	102.5	78.7
Total	436.2	409.9
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	3.1	2.0
1 year - 5 years	192.2	181.2
5 years - 10 years	75.6	63.0
10 years - 15 years	3.6	4.4
15 years - 20 years	1.5	1.6
20 years+	27.7	25.6
Total	$ 303.7	$ 277.8