Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair value of debt securities by contractual maturities
less than 1 year	$ 77.0	$ 94.0
1 year - 5 years	857.0	783.0
5 years - 10 years	704.0	681.0
10 years - 15 years	124.0	173.0
15 years - 20 years	50.0	79.0
20 years	343.0	275.0
Total	2,155.0	2,085.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
less than 1 year	1.8	14.9
1 year - 5 years	145.2	127.3
5 years - 10 years	138.5	128.2
10 years - 15 years	2.4	1.7
15 years - 20 years	2.0	1.0
20 years	14.0	9.5
Total	303.9	282.6
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
less than 1 year	27.1	12.0
1 year - 5 years	124.0	118.0
5 years - 10 years	114.3	112.5
10 years - 15 years	39.3	50.9
15 years - 20 years	26.5	24.2
20 years	78.7	68.2
Total	409.9	385.8
System Energy [Member]
Fair value of debt securities by contractual maturities
less than 1 year	2.0	33.5
1 year - 5 years	181.2	139.7
5 years - 10 years	63.0	53.5
10 years - 15 years	4.4	3.4
15 years - 20 years	1.6	3.2
20 years	25.6	22.0
Total	$ 277.8	$ 255.3