Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Entergy Arkansas [Member]	Dec. 31, 2012 Entergy Arkansas [Member]	Jun. 30, 2013 Entergy Gulf States Louisiana [Member]	Dec. 31, 2012 Entergy Gulf States Louisiana [Member]	Jun. 30, 2013 Entergy Louisiana [Member]	Jun. 30, 2012 Entergy Louisiana [Member]	Jun. 30, 2013 System Energy [Member]	Dec. 31, 2012 System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	$ 78.0	$ 53.0	$ 7.6	$ 8.8	$ 9.4	$ 8.0	$ 13.4	$ 1.9	$ 1.7	$ 1.3
1 year - 5 years	692.0	681.0	100.9	98.6	40.8	43.5	33.6	42.3	138.2	128.7
5 years - 10 years	555.0	562.0	115.2	93.1	63.3	63.5	25.6	24.9	51.1	53.9
10 years - 15 years	150.0	164.0	3.3	5.1	55.9	55.8	16.0	18.8	2.1	2.3
15 years - 20 years	64.0	61.0	0.9		8.9	8.5	2.4	1.7	1.6	1.4
20 years+	193.0	210.0	8.3	11.0	9.8	9.6	21.0	22.3	18.8	19.4
Total	$ 1,732.0	$ 1,731.0	$ 236.2	$ 216.6	$ 188.1	$ 188.9	$ 112.0	$ 111.9	$ 213.5	$ 207.0