Decommissioning Trust Funds (Securities Held) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 6,797.0	$ 5,724.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,902.0	1,707.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	16.0	28.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	4,389.0	3,511.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,857.0	1,673.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.0	1.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	2,408.0	2,213.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	45.0	34.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	15.0	27.0
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	884.3	834.7
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	311.3	284.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.3	4.2
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	556.3	525.4
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	308.0	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	328.0	309.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3.3	3.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.3	4.2
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,220.7	1,140.7
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	406.5	354.6
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.9	5.0
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	756.6	715.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	395.6	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	464.1	424.8
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	10.9	8.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.9	5.0
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	839.4	780.5
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	260.9	223.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.3	4.6
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	516.9	473.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	257.6	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	322.5	306.6
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3.3	2.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 2.3	$ 4.5