Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Fair value of debt securities by contractual maturities
Less than 1 year	$ 165.0	$ 199.0
1 year - 5 years	870.0	1,066.0
5 years - 10 years	636.0	544.0
10 years - 15 years	89.0	77.0
15 years - 20 years	98.0	78.0
20 years+	604.0	531.0
Total	2,462.0	2,495.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	50.3	32.5
1 year - 5 years	120.4	170.3
5 years - 10 years	144.5	114.0
10 years - 15 years	24.3	10.3
15 years - 20 years	14.2	8.1
20 years+	54.0	46.1
Total	407.7	381.3
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	56.6	31.1
1 year - 5 years	138.2	130.5
5 years - 10 years	118.4	111.0
10 years - 15 years	34.7	29.0
15 years - 20 years	45.0	37.1
20 years+	200.5	194.2
Total	593.4	532.9
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	11.2	22.8
1 year - 5 years	187.7	188.0
5 years - 10 years	92.7	73.4
10 years - 15 years	3.0	5.2
15 years - 20 years	5.9	10.2
20 years+	94.8	64.6
Total	$ 395.3	$ 364.2