Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair value of debt securities by contractual maturities
Less than 1 year	$ 84.0	$ 128.0
1 year - 5 years	798.0	807.0
5 years - 10 years	686.0	666.0
10 years - 15 years	226.0	125.0
15 years - 20 years	129.0	126.0
20 years+	600.0	604.0
Total	2,523.0	2,456.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	34.4	44.1
1 year - 5 years	108.2	109.1
5 years - 10 years	163.0	156.0
10 years - 15 years	43.8	31.3
15 years - 20 years	27.7	23.8
20 years+	40.7	48.5
Total	417.8	412.8
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	10.4	40.7
1 year - 5 years	143.3	142.0
5 years - 10 years	133.8	132.4
10 years - 15 years	62.2	39.8
15 years - 20 years	54.6	49.2
20 years+	198.7	197.4
Total	603.0	601.5
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	17.4	8.5
1 year - 5 years	163.9	154.6
5 years - 10 years	96.0	92.3
10 years - 15 years	20.8	13.4
15 years - 20 years	6.7	14.4
20 years+	103.2	103.0
Total	$ 408.0	$ 386.2