Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair value of debt securities by contractual maturities
less than 1 year	$ 199.0	$ 74.0
1 year - 5 years	1,066.0	902.0
5 years - 10 years	544.0	812.0
10 years - 15 years	77.0	147.0
15 years - 20 years	78.0	100.0
20 years	531.0	515.0
Total	2,495.0	2,550.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
less than 1 year	32.5	13.0
1 year - 5 years	170.3	123.4
5 years - 10 years	114.0	180.6
10 years - 15 years	10.3	4.8
15 years - 20 years	8.1	3.4
20 years	46.1	23.0
Total	381.3	348.2
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
less than 1 year	31.1	23.2
1 year - 5 years	130.5	122.8
5 years - 10 years	111.0	109.3
10 years - 15 years	29.0	52.7
15 years - 20 years	37.1	50.7
20 years	194.2	135.1
Total	532.9	493.8
System Energy [Member]
Fair value of debt securities by contractual maturities
less than 1 year	22.8	4.1
1 year - 5 years	188.0	173.0
5 years - 10 years	73.4	78.5
10 years - 15 years	5.2	1.0
15 years - 20 years	10.2	6.9
20 years	64.6	67.0
Total	$ 364.2	$ 330.5