Decommissioning Trust Funds (Securities Held) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 5,556.0	$ 5,350.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,575.0	1,437.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.0	19.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,283.0	3,195.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,467.0	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	2,273.0	2,155.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	108.0	41.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.0	17.0
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	802.8	771.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	258.4	238.5
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.2	2.4
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	497.6	467.4
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	246.3	234.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.1	0.2
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	305.2	303.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	12.1	4.1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.1	2.2
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,094.8	1,042.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	325.1	296.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.3	2.6
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	658.6	632.4
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	300.4	283.7
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.2
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	436.2	409.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	24.7	13.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.3	2.4
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	741.1	701.5
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	198.4	181.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.2	2.6
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	437.4	423.7
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	190.0	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	303.7	277.8
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	8.4	2.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 0.1	$ 2.3