Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Fair value of debt securities by contractual maturities
Less than 1 year	$ 36.0	$ 128.0
1 year - 5 years	775.0	807.0
5 years - 10 years	743.0	666.0
10 years - 15 years	309.0	125.0
15 years - 20 years	130.0	126.0
20 years+	592.0	604.0
Total	2,585.0	2,456.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	21.9	44.1
1 year - 5 years	104.2	109.1
5 years - 10 years	178.2	156.0
10 years - 15 years	67.9	31.3
15 years - 20 years	29.5	23.8
20 years+	39.8	48.5
Total	441.5	412.8
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	8.4	40.7
1 year - 5 years	142.4	142.0
5 years - 10 years	144.0	132.4
10 years - 15 years	80.4	39.8
15 years - 20 years	55.4	49.2
20 years+	192.3	197.4
Total	622.9	601.5
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year		8.5
1 year - 5 years	166.7	154.6
5 years - 10 years	103.4	92.3
10 years - 15 years	27.4	13.4
15 years - 20 years	6.5	14.4
20 years+	116.6	103.0
Total	418.8	$ 386.2
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, within One Year, Negative Fair Value	$ (1.8)