Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair value of debt securities by contractual maturities
Less than 1 year	$ 128.0	$ 199.0
1 year - 5 years	807.0	1,066.0
5 years - 10 years	666.0	544.0
10 years - 15 years	125.0	77.0
15 years - 20 years	126.0	78.0
20 years	604.0	531.0
Total	2,456.0	2,495.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	44.1	32.5
1 year - 5 years	109.1	170.3
5 years - 10 years	156.0	114.0
10 years - 15 years	31.3	10.3
15 years - 20 years	23.8	8.1
20 years	48.5	46.1
Total	412.8	381.3
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	40.7	31.1
1 year - 5 years	142.0	130.5
5 years - 10 years	132.4	111.0
10 years - 15 years	39.8	29.0
15 years - 20 years	49.2	37.1
20 years	197.4	194.2
Total	601.5	532.9
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	8.5	22.8
1 year - 5 years	154.6	188.0
5 years - 10 years	92.3	73.4
10 years - 15 years	13.4	5.2
15 years - 20 years	14.4	10.2
20 years	103.0	64.6
Total	$ 386.2	$ 364.2