Decommissioning Trust Funds (Securities Held) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Fair Value		$ 7,212.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		2,175.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		17.0
Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value		4,662.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		2,131.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		1.0
Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 2,448.0	2,550.0
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	10.0	44.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	51.0	16.0
Entergy Arkansas [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value		944.9
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		357.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		3.0
Entergy Arkansas [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value		596.7
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		354.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		0.0
Entergy Arkansas [Member] | Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	378.5	348.2
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0.2	2.1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	10.9	3.0
Entergy Louisiana [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value		1,312.1
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		472.1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		3.6
Entergy Louisiana [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value		818.3
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		461.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		0.0
Entergy Louisiana [Member] | Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	520.5	493.8
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2.0	10.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	9.3	3.6
System Energy [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value		905.7
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		312.8
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		1.2
System Energy [Member] | Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value		575.2
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax		308.6
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax		0.0
System Energy [Member] | Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fair Value	359.2	330.5
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0.9	4.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 7.1	$ 1.2