Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Fair value of debt securities by contractual maturities
Less than 1 year	$ 131.0	$ 74.0
1 year - 5 years	963.0	902.0
5 years - 10 years	693.0	812.0
10 years - 15 years	148.0	147.0
15 years - 20 years	105.0	100.0
20 years+	580.0	515.0
Total	2,620.0	2,550.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	29.5	13.0
1 year - 5 years	161.6	123.4
5 years - 10 years	115.4	180.6
10 years - 15 years	3.4	4.8
15 years - 20 years	5.9	3.4
20 years+	25.9	23.0
Total	341.7	348.2
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	29.5	23.2
1 year - 5 years	140.5	122.8
5 years - 10 years	101.7	109.3
10 years - 15 years	53.7	52.7
15 years - 20 years	45.0	50.7
20 years+	143.4	135.1
Total	513.8	493.8
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	9.7	4.1
1 year - 5 years	169.2	173.0
5 years - 10 years	71.6	78.5
10 years - 15 years	2.7	1.0
15 years - 20 years	11.3	6.9
20 years+	59.7	67.0
Total	$ 324.2	$ 330.5