Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Fair value of debt securities by contractual maturities
Less than 1 year	$ 71.0	$ 53.0
1 year - 5 years	692.0	681.0
5 years - 10 years	558.0	562.0
10 years - 15 years	161.0	164.0
15 years - 20 years	69.0	61.0
20 years+	197.0	210.0
Total	1,748.0	1,731.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	5.3	8.8
1 year - 5 years	115.2	98.6
5 years - 10 years	90.3	93.1
10 years - 15 years	4.0	5.1
15 years - 20 years	1.0
20 years+	7.6	11.0
Total	223.4	216.6
Entergy Gulf States Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	6.8	8.0
1 year - 5 years	40.9	43.5
5 years - 10 years	64.8	63.5
10 years - 15 years	58.0	55.8
15 years - 20 years	9.5	8.5
20 years+	11.5	9.6
Total	191.5	188.9
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	10.9	1.9
1 year - 5 years	34.8	42.3
5 years - 10 years	25.7	24.9
10 years - 15 years	17.4	18.8
15 years - 20 years	2.3	1.7
20 years+	21.3	22.3
Total	112.4	111.9
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	6.5	1.3
1 year - 5 years	119.5	128.7
5 years - 10 years	62.7	53.9
10 years - 15 years	2.4	2.3
15 years - 20 years	1.7	1.4
20 years+	17.3	19.4
Total	$ 210.1	$ 207.0