Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Fair value of debt securities by contractual maturities
Less than 1 year	$ 106.0	$ 125.0
1 year - 5 years	805.0	763.0
5 years - 10 years	795.0	719.0
10 years - 15 years	111.0	109.0
15 years - 20 years	88.0	73.0
20 years+	503.0	424.0
Total	2,408.0	2,213.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	16.8	16.7
1 year - 5 years	102.6	106.2
5 years - 10 years	183.5	161.2
10 years - 15 years	4.4	7.7
15 years - 20 years	1.1	1.0
20 years+	19.6	16.5
Total	328.0	309.3
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	28.5	31.4
1 year - 5 years	105.2	99.1
5 years - 10 years	131.9	122.8
10 years - 15 years	44.3	41.4
15 years - 20 years	38.6	30.9
20 years+	115.6	99.2
Total	464.1	424.8
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	8.6	6.6
1 year - 5 years	159.6	188.2
5 years - 10 years	86.4	78.5
10 years - 15 years	2.3	1.3
15 years - 20 years	7.8	7.8
20 years+	57.8	24.2
Total	$ 322.5	$ 306.6