Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Fair value of debt securities by contractual maturities
Less than 1 year	$ 102.0	$ 77.0
1 year - 5 years	812.0	857.0
5 years - 10 years	743.0	704.0
10 years - 15 years	128.0	124.0
15 years - 20 years	62.0	50.0
20 years+	444.0	343.0
Total	2,291.0	2,155.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	8.8	1.8
1 year - 5 years	123.5	145.2
5 years - 10 years	166.1	138.5
10 years - 15 years	9.5	2.4
15 years - 20 years	1.1	2.0
20 years+	9.9	14.0
Total	318.9	303.9
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	25.0	27.1
1 year - 5 years	102.3	124.0
5 years - 10 years	121.5	114.3
10 years - 15 years	51.0	39.3
15 years - 20 years	31.1	26.5
20 years+	109.2	78.7
Total	440.1	409.9
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	3.0	2.0
1 year - 5 years	192.6	181.2
5 years - 10 years	76.2	63.0
10 years - 15 years	3.5	4.4
15 years - 20 years	1.5	1.6
20 years+	31.8	25.6
Total	$ 308.6	$ 277.8