Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair value of debt securities by contractual maturities
Less than 1 year		$ 128.0
1 year - 5 years	$ 672.0	807.0
5 years - 10 years	852.0	666.0
10 years - 15 years	377.0	125.0
15 years - 20 years	144.0	126.0
20 years+	576.0	604.0
Total	2,617.0	2,456.0
Debt Securities Available For Sale Maturity Allocated And Single Maturity Date Within One Year Negative Fair Value	(4.0)
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	0.0	44.1
1 year - 5 years	113.1	109.1
5 years - 10 years	189.8	156.0
10 years - 15 years	81.4	31.3
15 years - 20 years	28.5	23.8
20 years+	35.1	48.5
Total	447.9	412.8
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	0.0	40.7
1 year - 5 years	117.0	142.0
5 years - 10 years	159.4	132.4
10 years - 15 years	101.2	39.8
15 years - 20 years	66.9	49.2
20 years+	187.7	197.4
Total	632.2	601.5
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year		8.5
1 year - 5 years	134.7	154.6
5 years - 10 years	141.5	92.3
10 years - 15 years	31.5	13.4
15 years - 20 years	5.3	14.4
20 years+	115.8	103.0
Total	427.7	$ 386.2
Debt Securities Available For Sale Maturity Allocated And Single Maturity Date Within One Year Negative Fair Value	$ (1.1)