Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair value of debt securities by contractual maturities
Less than 1 year	$ 53.0	$ 69.0
1 year - 5 years	681.0	566.0
5 years - 10 years	562.0	583.0
10 years - 15 years	164.0	187.0
15 years - 20 years	61.0	42.0
20 years+	210.0	212.0
Total	1,731.0	1,659.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	8.8	7.8
1 year - 5 years	98.6	86.5
5 years - 10 years	93.1	109.1
10 years - 15 years	5.1	2.7
20 years+	11.0	6.2
Total	216.6	212.3
Entergy Gulf States Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	8.0	7.1
1 year - 5 years	43.5	40.8
5 years - 10 years	63.5	53.5
10 years - 15 years	55.8	62.9
15 years - 20 years	8.5	3.2
20 years+	9.6	14.7
Total	188.9	182.2
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	1.9	3.9
1 year - 5 years	42.3	39.8
5 years - 10 years	24.9	22.2
10 years - 15 years	18.8	18.9
15 years - 20 years	1.7	2.2
20 years+	22.3	17.8
Total	111.9	104.8
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	1.3	10.2
1 year - 5 years	128.7	94.6
5 years - 10 years	53.9	57.9
10 years - 15 years	2.3	2.6
15 years - 20 years	1.4	2.9
20 years+	19.4	18.0
Total	$ 207.0	$ 186.2