Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair value of debt securities by contractual maturities
Less than 1 year	$ 64.0	$ 69.0
1 year - 5 years	619.0	566.0
5 years - 10 years	555.0	583.0
10 years - 15 years	208.0	187.0
15 years - 20 years	47.0	42.0
20 years+	194.0	212.0
Total	1,687.0	1,659.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	12.7	7.8
1 year - 5 years	90.4	86.5
5 years - 10 years	106.5	109.1
10 years - 15 years	5.3	2.7
20 years+	5.3	6.2
Total	220.2	212.3
Entergy Gulf States Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	2.8	7.1
1 year - 5 years	46.1	40.8
5 years - 10 years	54.6	53.5
10 years - 15 years	68.0	62.9
15 years - 20 years	3.8	3.2
20 years+	7.7	14.7
Total	183.0	182.2
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	4.0	3.9
1 year - 5 years	39.5	39.8
5 years - 10 years	24.7	22.2
10 years - 15 years	19.5	18.9
15 years - 20 years	1.7	2.2
20 years+	19.9	17.8
Total	109.3	104.8
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	23.7	10.2
1 year - 5 years	96.9	94.6
5 years - 10 years	53.5	57.9
10 years - 15 years	1.8	2.6
15 years - 20 years	2.1	2.9
20 years+	17.4	18.0
Total	$ 195.4	$ 186.2