Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair value of debt securities by contractual maturities
Less than 1 year	$ 46.0	$ 69.0
1 year - 5 years	666.0	566.0
5 years - 10 years	557.0	583.0
10 years - 15 years	188.0	187.0
15 years - 20 years	53.0	42.0
20 years+	213.0	212.0
Total	1,723.0	1,659.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	12.6	7.8
1 year - 5 years	101.0	86.5
5 years - 10 years	95.7	109.1
10 years - 15 years	4.8	2.7
20 years+	7.0	6.2
Total	221.1	212.3
Entergy Gulf States Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	6.3	7.1
1 year - 5 years	42.1	40.8
5 years - 10 years	56.3	53.5
10 years - 15 years	65.6	62.9
15 years - 20 years	6.0	3.2
20 years+	9.3	14.7
Total	185.6	182.2
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	2.6	3.9
1 year - 5 years	40.6	39.8
5 years - 10 years	24.9	22.2
10 years - 15 years	19.7	18.9
15 years - 20 years	1.0	2.2
20 years+	22.7	17.8
Total	111.5	104.8
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	5.5	10.2
1 year - 5 years	121.0	94.6
5 years - 10 years	53.8	57.9
10 years - 15 years	1.6	2.6
15 years - 20 years	2.2	2.9
20 years+	20.1	18.0
Total	$ 204.2	$ 186.2