Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair value of debt securities by contractual maturities
Less than 1 year	$ 119.0	$ 74.0
1 year - 5 years	934.0	902.0
5 years - 10 years	628.0	812.0
10 years - 15 years	108.0	147.0
15 years - 20 years	92.0	100.0
20 years+	567.0	515.0
Total	2,448.0	2,550.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	40.8	13.0
1 year - 5 years	174.4	123.4
5 years - 10 years	115.6	180.6
10 years - 15 years	10.6	4.8
15 years - 20 years	5.8	3.4
20 years+	31.3	23.0
Total	378.5	348.2
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	22.4	23.2
1 year - 5 years	122.0	122.8
5 years - 10 years	117.9	109.3
10 years - 15 years	37.7	52.7
15 years - 20 years	41.3	50.7
20 years+	179.2	135.1
Total	520.5	493.8
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	2.2	4.1
1 year - 5 years	195.4	173.0
5 years - 10 years	78.2	78.5
10 years - 15 years	5.6	1.0
15 years - 20 years	11.0	6.9
20 years+	66.8	67.0
Total	$ 359.2	$ 330.5