Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair value of debt securities by contractual maturities
Less than 1 year	$ 109.0	$ 53.0
1 year - 5 years	679.0	681.0
5 years - 10 years	574.0	562.0
10 years - 15 years	145.0	164.0
15 years - 20 years	59.0	61.0
20 years+	174.0	210.0
Total	1,740.0	1,731.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	8.2	8.8
1 year - 5 years	100.5	98.6
5 years - 10 years	122.3	93.1
10 years - 15 years	3.3	5.1
15 years - 20 years	0.9
20 years+	3.8	11.0
Total	239.0	216.6
Entergy Gulf States Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	8.0	8.0
1 year - 5 years	41.7	43.5
5 years - 10 years	71.5	63.5
10 years - 15 years	52.8	55.8
15 years - 20 years	6.5	8.5
20 years+	9.9	9.6
Total	190.4	188.9
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	14.4	1.9
1 year - 5 years	32.0	42.3
5 years - 10 years	35.6	24.9
10 years - 15 years	6.5	18.8
15 years - 20 years	4.5	1.7
20 years+	17.7	22.3
Total	110.7	111.9
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	10.4	1.3
1 year - 5 years	132.4	128.7
5 years - 10 years	51.0	53.9
10 years - 15 years	6.3	2.3
15 years - 20 years	2.0	1.4
20 years+	17.5	19.4
Total	$ 219.6	$ 207.0