Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	$ 28.0	$ 19.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	23.0	54.0
More than 12 months Fair Value	1.0	1.0
Total Fair Value	24.0	55.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	1.0	2.0
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	2.0
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	1,169.0	1,031.0
More than 12 months Fair Value	20.0	61.0
Total Fair Value	1,189.0	1,092.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	27.0	17.0
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	26.0	15.0
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	1.0	2.0
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.2	2.4
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.0	7.8
More than 12 months Fair Value	0.0	0.0
Total Fair Value	0.0	7.8
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.2
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	0.2
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	146.7	111.4
More than 12 months Fair Value	0.0	18.5
Total Fair Value	146.7	129.9
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.2	2.2
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	4.2	1.7
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	0.0	0.5
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5.0	2.6
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.0	9.4
More than 12 months Fair Value	0.0	0.0
Total Fair Value	0.0	9.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.0	0.2
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	0.2
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	198.8	124.0
More than 12 months Fair Value	4.8	7.4
Total Fair Value	203.6	131.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	5.0	2.4
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	4.8	2.0
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	0.2	0.4
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.6	2.6
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.0	8.3
More than 12 months Fair Value	0.0	0.9
Total Fair Value	0.0	9.2
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0.1	0.3
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	0.2
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	0.1	0.1
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	220.9	200.4
More than 12 months Fair Value	0.8	5.0
Total Fair Value	221.7	205.4
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	4.5	2.3
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	4.4	2.2
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	$ 0.1	$ 0.1