Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Fair value of debt securities by contractual maturities
Less than 1 year	$ 53.0	$ 94.0
1 year - 5 years	767.0	783.0
5 years - 10 years	762.0	681.0
10 years - 15 years	191.0	173.0
15 years - 20 years	71.0	79.0
20 years+	329.0	275.0
Total	2,173.0	2,085.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	1.3	14.9
1 year - 5 years	129.9	127.3
5 years - 10 years	151.7	128.2
10 years - 15 years	4.9	1.7
15 years - 20 years	1.5	1.0
20 years+	13.8	9.5
Total	303.1	282.6
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	9.6	5.6
1 year - 5 years	55.1	58.2
5 years - 10 years	46.2	44.2
10 years - 15 years	11.6	7.3
15 years - 20 years	9.8	9.4
20 years+	19.0	19.3
Total	151.3	144.0
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	8.9	33.5
1 year - 5 years	157.5	139.7
5 years - 10 years	77.2	53.5
10 years - 15 years	4.8	3.4
15 years - 20 years	1.6	3.2
20 years+	25.4	22.0
Total	$ 275.4	$ 255.3