Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 17.0	$ 28.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	8.0	23.0
More than 12 months Fair Value	0.0	1.0
Total Fair Value	8.0	24.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.0	1.0
Equity Securities [Member] | Less than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.0	1.0
Equity Securities [Member] | More than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	1,099.0	1,169.0
More than 12 months Fair Value	265.0	20.0
Total Fair Value	1,364.0	1,189.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	16.0	27.0
Debt Securities [Member] | Less than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	7.0	26.0
Debt Securities [Member] | More than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	9.0	1.0
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3.0	4.2
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.0	0.0
More than 12 months Fair Value	0.0	0.0
Total Fair Value	0.0	0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.0
Entergy Arkansas [Member] | Equity Securities [Member] | Less than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.0
Entergy Arkansas [Member] | Equity Securities [Member] | More than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
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]
Less than 12 months Fair Value	168.0	146.7
More than 12 months Fair Value	41.4	0.0
Total Fair Value	209.4	146.7
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3.0	4.2
Entergy Arkansas [Member] | Debt Securities [Member] | Less than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.2	4.2
Entergy Arkansas [Member] | Debt Securities [Member] | More than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.8	0.0
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3.6	5.0
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.0	0.0
More than 12 months Fair Value	0.0	0.0
Total Fair Value	0.0	0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.0
Entergy Louisiana [Member] | Equity Securities [Member] | Less than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.0
Entergy Louisiana [Member] | Equity Securities [Member] | More than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
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]
Less than 12 months Fair Value	135.3	198.8
More than 12 months Fair Value	84.4	4.8
Total Fair Value	219.7	203.6
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	3.6	5.0
Entergy Louisiana [Member] | Debt Securities [Member] | Less than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.1	4.8
Entergy Louisiana [Member] | Debt Securities [Member] | More than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.5	0.2
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.2	4.6
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.0	0.0
More than 12 months Fair Value	0.0	0.0
Total Fair Value	0.0	0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.1
System Energy [Member] | Equity Securities [Member] | Less than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.0
System Energy [Member] | Equity Securities [Member] | More than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
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]
Less than 12 months Fair Value	196.9	220.9
More than 12 months Fair Value	10.4	0.8
Total Fair Value	207.3	221.7
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.2	4.5
System Energy [Member] | Debt Securities [Member] | Less than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.0	4.4
System Energy [Member] | Debt Securities [Member] | More than 12 Months [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 0.2	$ 0.1