Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair value of debt securities by contractual maturities
less than 1 year	$ 94.0	$ 83.0
1 year - 5 years	783.0	752.0
5 years - 10 years	681.0	620.0
10 years - 15 years	173.0	169.0
15 years - 20 years	79.0	52.0
20 years	275.0	154.0
Total	2,085.0	1,830.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
less than 1 year	14.9	8.1
1 year - 5 years	127.3	110.9
5 years - 10 years	128.2	118.0
10 years - 15 years	1.7	3.9
15 years - 20 years	1.0	0.9
20 years	9.5	5.8
Total	282.6	247.6
Entergy Gulf States Louisiana [Member]
Fair value of debt securities by contractual maturities
less than 1 year	6.4	7.9
1 year - 5 years	59.8	51.2
5 years - 10 years	68.3	75.5
10 years - 15 years	43.6	55.8
15 years - 20 years	14.8	4.6
20 years	48.9	7.9
Total	241.8	202.9
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
less than 1 year	5.6	14.8
1 year - 5 years	58.2	41.9
5 years - 10 years	44.2	37.0
10 years - 15 years	7.3	6.6
15 years - 20 years	9.4	6.2
20 years	19.3	16.6
Total	144.0	123.1
System Energy [Member]
Fair value of debt securities by contractual maturities
less than 1 year	33.5	5.5
1 year - 5 years	139.7	144.9
5 years - 10 years	53.5	44.3
10 years - 15 years	3.4	9.3
15 years - 20 years	3.2	1.6
20 years	22.0	18.3
Total	$ 255.3	$ 223.9