Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair value of debt securities by contractual maturities
1 year - 5 years	$ 1,027.0	$ 672.0
5 years - 10 years	1,257.0	852.0
10 years - 15 years	492.0	377.0
15 years - 20 years	128.0	144.0
20 years+	532.0	576.0
Total	3,436.0	2,617.0
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	0.0
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
1 year - 5 years	84.7	113.1
5 years - 10 years	179.2	189.8
10 years - 15 years	100.8	81.4
15 years - 20 years	26.7	28.5
20 years+	34.5	35.1
Total	425.9	447.9
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	0.0	0.0
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
1 year - 5 years	89.3	117.0
5 years - 10 years	186.0	159.4
10 years - 15 years	113.7	101.2
15 years - 20 years	63.4	66.9
20 years+	180.4	187.7
Total	632.8	632.2
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	0.0	0.0
System Energy [Member]
Fair value of debt securities by contractual maturities
1 year - 5 years	136.2	134.7
5 years - 10 years	120.4	141.5
10 years - 15 years	35.1	31.5
15 years - 20 years	4.5	5.3
20 years+	110.2	115.8
Total	406.4	427.7
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, within One Year, Negative Fair Value	$ 0.0	$ (1.1)