Decommissioning Trust Funds (Securities Held) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 6,669.0	$ 5,724.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,858.0	1,707.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	27.0	28.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	4,439.0	3,511.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,823.0	1,673.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5.0	1.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	2,230.0	2,213.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	35.0	34.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	22.0	27.0
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	867.7	834.7
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	310.3	284.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3.6	4.2
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	557.7	525.4
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	307.2	281.5
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.0
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	310.0	309.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3.1	3.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3.6	4.2
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,190.1	1,140.7
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	391.2	354.6
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.3	5.0
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	750.6	715.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	382.7	346.6
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.0
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	439.5	424.8
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	8.5	8.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.3	5.0
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	816.0	780.5
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	247.8	223.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3.4	4.6
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	509.0	473.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	245.4	221.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.1
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	307.0	306.6
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2.4	2.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 3.4	$ 4.5