Decommissioning Trust Funds (Securities Held) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 5,724.0	$ 5,350.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,707.0	1,437.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	28.0	19.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,511.0	3,195.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,673.0	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	2,213.0	2,155.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	34.0	41.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	27.0	17.0
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,140.7	1,042.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	354.6	296.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5.0	2.6
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	715.9	632.4
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	346.6	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	424.8	409.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	8.0	13.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5.0	2.4
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	834.7	771.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	284.9	238.5
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.2	2.4
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	525.4	467.4
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	281.5	234.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.2
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	309.3	303.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3.4	4.1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.2	2.2
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	780.5	701.5
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	223.9	181.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.6	2.6
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	473.9	423.7
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	221.9	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	306.6	277.8
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2.0	2.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 4.5	$ 2.3