Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Fair value of debt securities by contractual maturities
1 year - 5 years	$ 455.0	$ 672.0
5 years - 10 years	663.0	852.0
10 years - 15 years	335.0	377.0
15 years - 20 years	117.0	144.0
20 years+	468.0	576.0
Total	2,038.0	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	93.6	113.1
5 years - 10 years	191.6	189.8
10 years - 15 years	121.5	81.4
15 years - 20 years	28.8	28.5
20 years+	37.0	35.1
Total	472.5	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	122.7	117.0
5 years - 10 years	188.4	159.4
10 years - 15 years	103.5	101.2
15 years - 20 years	74.3	66.9
20 years+	208.6	187.7
Total	697.5	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	144.0	134.7
5 years - 10 years	147.3	141.5
10 years - 15 years	46.3	31.5
15 years - 20 years	2.8	5.3
20 years+	127.4	115.8
Total	467.8	427.7
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		$ (1.1)