Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 19.0	$ 7.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	54.0	9.0
More than 12 months Fair Value	1.0	0.0
Total Fair Value	55.0	9.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.0	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	2.0	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	1,031.0	277.0
More than 12 months Fair Value	61.0	163.0
Total Fair Value	1,092.0	440.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	17.0	6.0
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	15.0	2.0
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	2.0	4.0
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.4	1.1
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	7.8	0.0
More than 12 months Fair Value	0.0	0.0
Total Fair Value	7.8	0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.2	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	111.4	56.5
More than 12 months Fair Value	18.5	34.8
Total Fair Value	129.9	91.3
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.2	1.1
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	1.7	0.0
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	0.5	0.8
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.6	0.7
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	9.4	0.0
More than 12 months Fair Value	0.0	0.0
Total Fair Value	9.4	0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.2	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	124.0	33.1
More than 12 months Fair Value	7.4	27.1
Total Fair Value	131.4	60.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.4	0.7
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	2.0	0.0
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	0.0	0.5
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.6	0.3
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	8.3	0.0
More than 12 months Fair Value	0.9	0.0
Total Fair Value	9.2	0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.3	0.0
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	0.0
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	200.4	51.6
More than 12 months Fair Value	5.0	6.5
Total Fair Value	205.4	58.1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	2.3	0.3
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	2.2	0.0
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	$ 0.0	$ 0.0