Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Fair value of debt securities by contractual maturities
Less than 1 year	$ 98.0	$ 77.0
1 year - 5 years	855.0	857.0
5 years - 10 years	711.0	704.0
10 years - 15 years	144.0	124.0
15 years - 20 years	58.0	50.0
20 years+	383.0	343.0
Total	2,249.0	2,155.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	3.7	1.8
1 year - 5 years	142.0	145.2
5 years - 10 years	138.4	138.5
10 years - 15 years	7.5	2.4
15 years - 20 years	2.1	2.0
20 years+	17.5	14.0
Total	311.2	303.9
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	31.9	27.1
1 year - 5 years	114.8	124.0
5 years - 10 years	121.2	114.3
10 years - 15 years	43.6	39.3
15 years - 20 years	29.7	26.5
20 years+	81.0	78.7
Total	422.2	409.9
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	4.6	2.0
1 year - 5 years	180.9	181.2
5 years - 10 years	73.3	63.0
10 years - 15 years	4.5	4.4
15 years - 20 years	1.5	1.6
20 years+	26.6	25.6
Total	$ 291.4	$ 277.8