Decommissioning Trust Funds (Fair Value Of Debt Securities By Contractual Maturities) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair value of debt securities by contractual maturities
Less than 1 year	$ 99.0	$ 125.0
1 year - 5 years	783.0	763.0
5 years - 10 years	742.0	719.0
10 years - 15 years	113.0	109.0
15 years - 20 years	69.0	73.0
20 years+	424.0	424.0
Total	2,230.0	2,213.0
Entergy Arkansas [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	17.8	16.7
1 year - 5 years	109.7	106.2
5 years - 10 years	162.1	161.2
10 years - 15 years	7.0	7.7
15 years - 20 years	1.0	1.0
20 years+	12.4	16.5
Total	310.0	309.3
Entergy Louisiana [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	28.1	31.4
1 year - 5 years	101.2	99.1
5 years - 10 years	126.4	122.8
10 years - 15 years	44.0	41.4
15 years - 20 years	30.3	30.9
20 years+	109.5	99.2
Total	439.5	424.8
System Energy [Member]
Fair value of debt securities by contractual maturities
Less than 1 year	1.7	6.6
1 year - 5 years	188.5	188.2
5 years - 10 years	84.6	78.5
10 years - 15 years	1.4	1.3
15 years - 20 years	7.6	7.8
20 years+	23.2	24.2
Total	$ 307.0	$ 306.6