Decommissioning Trust Funds (Securities Held) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 5,350.0	$ 5,371.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,437.0	1,589.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	19.0	7.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,195.0	3,286.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,396.0	1,513.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.0	1.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	2,155.0	2,085.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	41.0	76.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	17.0	6.0
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,042.3	1,021.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	296.9	313.1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.6	0.7
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	632.4	635.5
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	283.7	294.3
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.2	0.0
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	409.9	385.8
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	13.2	18.8
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.4	0.7
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	771.3	769.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	238.5	255.1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.4	1.1
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	467.4	487.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	234.4	248.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.2	0.0
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	303.9	282.6
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	4.1	6.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.2	1.1
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	701.5	679.8
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	181.4	193.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.6	0.3
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	423.7	424.5
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	179.2	188.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.3	0.0
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	277.8	255.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2.2	5.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 2.3	$ 0.3