Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	$ 3.0	$ 37.0
More than 12 months Fair Value		20.0
Total Fair Value	3.0	57.0
Less than 12 Months Gross Unrealized Losses		1.0
Total Gross Unrealized Losses		1.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	223.0	175.0
More than 12 months Fair Value	36.0	48.0
Total Fair Value	259.0	223.0
Less than 12 Months Gross Unrealized Losses	2.0	1.0
More than 12 Months Gross Unrealized Losses	3.0	4.0
Total Gross Unrealized Losses	5.0	5.0
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value		0.2
Total Fair Value		0.2
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	35.5	24.4
More than 12 months Fair Value	2.0	1.0
Total Fair Value	37.5	25.4
Less than 12 Months Gross Unrealized Losses	0.4	0.2
More than 12 Months Gross Unrealized Losses	0.1
Total Gross Unrealized Losses	0.5	0.2
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value		1.2
More than 12 months Fair Value		1.0
Total Fair Value		2.2
Entergy Gulf States Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	18.4	9.1
Total Fair Value	18.4	9.1
Less than 12 Months Gross Unrealized Losses	0.3	0.1
Total Gross Unrealized Losses	0.3	0.1
Entergy Louisiana [Member] | Equity Securities [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
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	9.5	3.4
More than 12 months Fair Value	0.5	0.5
Total Fair Value	10.0	3.9
Less than 12 Months Gross Unrealized Losses	0.1
More than 12 Months Gross Unrealized Losses	0.1	0.1
Total Gross Unrealized Losses	0.2	0.1
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value		1.4
More than 12 months Fair Value		13.0
Total Fair Value		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	17.0	15.5
Total Fair Value	17.0	15.5
Less than 12 Months Gross Unrealized Losses	0.1	0.1
Total Gross Unrealized Losses	$ 0.1	$ 0.1