Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair value of debt securities by contractual maturities
1 year - 5 years	$ 431.0	$ 672.0
5 years - 10 years	679.0	852.0
10 years - 15 years	346.0	377.0
15 years - 20 years	122.0	144.0
20 years+	477.0	576.0
Total	2,055.0	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	74.2	113.1
5 years - 10 years	207.3	189.8
10 years - 15 years	131.6	81.4
15 years - 20 years	31.3	28.5
20 years+	33.5	35.1
Total	477.9	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	117.0	117.0
5 years - 10 years	191.0	159.4
10 years - 15 years	109.5	101.2
15 years - 20 years	77.6	66.9
20 years+	210.7	187.7
Total	705.8	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	149.2	134.7
5 years - 10 years	147.0	141.5
10 years - 15 years	40.2	31.5
15 years - 20 years	1.2	5.3
20 years+	130.4	115.8
Total	468.0	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)