Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	$ 24.0	$ 130.0
More than 12 months Fair Value	13.0	43.0
Total Fair Value	37.0	173.0
Less than 12 Months Gross Unrealized Losses	2.0	9.0
More than 12 Months Gross Unrealized Losses		5.0
Total Gross Unrealized Losses	2.0	14.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	81.0	123.0
More than 12 months Fair Value	50.0	60.0
Total Fair Value	131.0	183.0
Less than 12 Months Gross Unrealized Losses	1.0	3.0
More than 12 Months Gross Unrealized Losses	3.0	2.0
Total Gross Unrealized Losses	4.0	5.0
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.1	13.7
Total Fair Value	0.1	13.7
Less than 12 Months Gross Unrealized Losses		0.4
Total Gross Unrealized Losses		0.4
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	10.1	14.3
More than 12 months Fair Value	1.0	1.0
Total Fair Value	11.1	15.3
Less than 12 Months Gross Unrealized Losses	0.1	0.4
Total Gross Unrealized Losses	0.1	0.4
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.1	14.0
More than 12 months Fair Value	0.5	2.7
Total Fair Value	0.6	16.7
Less than 12 Months Gross Unrealized Losses		0.5
More than 12 Months Gross Unrealized Losses		0.3
Total Gross Unrealized Losses		0.8
Entergy Gulf States Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	1.8	9.3
More than 12 months Fair Value		1.1
Total Fair Value	1.8	10.4
Less than 12 Months Gross Unrealized Losses		0.2
More than 12 Months Gross Unrealized Losses		0.1
Total Gross Unrealized Losses		0.3
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.1	11.6
More than 12 months Fair Value	2.8	10.0
Total Fair Value	2.9	21.6
Less than 12 Months Gross Unrealized Losses		0.3
More than 12 Months Gross Unrealized Losses		1.3
Total Gross Unrealized Losses		1.6
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	1.4	5.5
More than 12 months Fair Value	0.6	0.2
Total Fair Value	2.0	5.7
Less than 12 Months Gross Unrealized Losses		0.2
More than 12 Months Gross Unrealized Losses	0.1
Total Gross Unrealized Losses	0.1	0.2
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.7	41.3
More than 12 months Fair Value	8.3	30.0
Total Fair Value	9.0	71.3
Less than 12 Months Gross Unrealized Losses		1.8
More than 12 Months Gross Unrealized Losses	0.1	3.6
Total Gross Unrealized Losses	0.1	5.4
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	11.6	10.5
Total Fair Value	11.6	10.5
Less than 12 Months Gross Unrealized Losses		0.1
Total Gross Unrealized Losses		$ 0.1