Decommissioning Trust Funds (Securities Held) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 5,452.0	$ 5,350.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,716.0	1,437.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5.0	19.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,203.0	3,195.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,638.0	1,396.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.0	2.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	2,249.0	2,155.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	78.0	41.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.0	17.0
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	785.5	771.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	248.0	238.5
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.0	2.4
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	474.3	467.4
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	238.5	234.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.2	0.2
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	311.2	303.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	9.5	4.1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.8	2.2
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,065.2	1,042.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	308.3	296.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.9	2.6
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	643.0	632.4
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	289.3	283.7
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.1	0.2
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	422.2	409.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	19.0	13.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.8	2.4
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	719.8	701.5
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	188.2	181.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.5	2.6
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	428.4	423.7
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	182.7	179.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.1	0.3
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	291.4	277.8
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	5.5	2.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 0.4	$ 2.3