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Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) (USD $)
In Millions, unless otherwise specified
9 Months Ended 12 Months Ended
Sep. 30, 2013
Dec. 31, 2012
Equity Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value $ 19.0 $ 37.0
More than 12 months Fair Value   20.0
Total Fair Value 19.0 57.0
Less than 12 Months Gross Unrealized Losses 1.0 1.0
Total Gross Unrealized Losses 1.0 1.0
Debt Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value 589.0 175.0
More than 12 months Fair Value 39.0 48.0
Total Fair Value 628.0 223.0
Less than 12 Months Gross Unrealized Losses 21.0 1.0
More than 12 Months Gross Unrealized Losses 3.0 4.0
Total Gross Unrealized Losses 24.0 5.0
Entergy Arkansas [Member] | Equity Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value 0.1 0.2
Total Fair Value 0.1 0.2
Entergy Arkansas [Member] | Debt Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value 123.7 24.4
More than 12 months Fair Value 3.3 1.0
Total Fair Value 127.0 25.4
Less than 12 Months Gross Unrealized Losses 3.9 0.2
More than 12 Months Gross Unrealized Losses 0.2  
Total Gross Unrealized Losses 4.1 0.2
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value 0.4 1.2
More than 12 months Fair Value   1.0
Total Fair Value 0.4 2.2
Entergy Gulf States Louisiana [Member] | Debt Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value 60.0 9.1
Total Fair Value 60.0 9.1
Less than 12 Months Gross Unrealized Losses 2.6 0.1
Total Gross Unrealized Losses 2.6 0.1
Entergy Louisiana [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value   0.7
More than 12 months Fair Value   5.6
Total Fair Value   6.3
Entergy Louisiana [Member] | Equity Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value 0.1  
Total Fair Value 0.1  
More than 12 Months Gross Unrealized Losses   0.1
Total Gross Unrealized Losses   0.1
Entergy Louisiana [Member] | Debt Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value 29.0 3.4
More than 12 months Fair Value 0.6 0.5
Total Fair Value 29.6 3.9
Less than 12 Months Gross Unrealized Losses 1.4  
More than 12 Months Gross Unrealized Losses 0.1 0.1
Total Gross Unrealized Losses 1.5 0.1
System Energy [Member] | Equity Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value 0.2 1.4
More than 12 months Fair Value   13.0
Total Fair Value 0.2 14.4
More than 12 Months Gross Unrealized Losses   0.2
Total Gross Unrealized Losses   0.2
System Energy [Member] | Debt Securities [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Less than 12 months Fair Value 52.9 15.5
Total Fair Value 52.9 15.5
Less than 12 Months Gross Unrealized Losses 1.2 0.1
Total Gross Unrealized Losses $ 1.2 $ 0.1