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Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) - USD ($)
$ in Millions
Dec. 31, 2018
Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   $ 17.0
Less than 12 months Fair Value $ 652.0 1,099.0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 9.0 7.0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer 782.0 265.0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 26.0 9.0
Debt Securities, Available-for-sale, Unrealized Loss Position 1,434.0 1,364.0
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss 35.0 16.0
Equity Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value   8.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   1.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value   0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value   8.0
Equity Securities [Member] | Less than 12 Months [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   1.0
Equity Securities [Member] | More than 12 Months [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   0.0
Entergy Arkansas [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   3.0
Less than 12 months Fair Value 65.8 168.0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 0.5 1.2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer 231.1 41.4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 7.7 1.8
Debt Securities, Available-for-sale, Unrealized Loss Position 296.9 209.4
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss 8.2 3.0
Entergy Arkansas [Member] | Equity Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value   0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value   0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value   0.0
Entergy Arkansas [Member] | Equity Securities [Member] | Less than 12 Months [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   0.0
Entergy Arkansas [Member] | Equity Securities [Member] | More than 12 Months [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   0.0
Entergy Louisiana [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   3.6
Less than 12 months Fair Value 170.1 135.3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 2.1 1.1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer 145.8 84.4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 3.9 2.5
Debt Securities, Available-for-sale, Unrealized Loss Position 315.9 219.7
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss 6.0 3.6
Entergy Louisiana [Member] | Equity Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value   0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value   0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value   0.0
Entergy Louisiana [Member] | Equity Securities [Member] | Less than 12 Months [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   0.0
Entergy Louisiana [Member] | Equity Securities [Member] | More than 12 Months [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   0.0
System Energy [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   1.2
Less than 12 months Fair Value 89.7 196.9
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 2.4 1.0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer 79.8 10.4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 3.4 0.0
Debt Securities, Available-for-sale, Unrealized Loss Position 169.5 207.3
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss $ 5.8 1.2
System Energy [Member] | Equity Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value   0.0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value   0.0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value   0.0
System Energy [Member] | Equity Securities [Member] | Less than 12 Months [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   0.0
System Energy [Member] | Equity Securities [Member] | More than 12 Months [Member]    
Debt Securities, Available-for-sale [Line Items]    
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax   $ 0.0