Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	$ 37.0	$ 130.0
More than 12 months Fair Value	20.0	43.0
Total Fair Value	57.0	173.0
Less than 12 Months Gross Unrealized Losses	1.0	9.0
More than 12 Months Gross Unrealized Losses		5.0
Total Gross Unrealized Losses	1.0	14.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	175.0	123.0
More than 12 months Fair Value	48.0	60.0
Total Fair Value	223.0	183.0
Less than 12 Months Gross Unrealized Losses	1.0	3.0
More than 12 Months Gross Unrealized Losses	4.0	2.0
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	13.7
Total Fair Value	0.2	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	24.4	14.3
More than 12 months Fair Value	1.0	1.0
Total Fair Value	25.4	15.3
Less than 12 Months Gross Unrealized Losses	0.2	0.4
Total Gross Unrealized Losses	0.2	0.4
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	1.2	14.0
More than 12 months Fair Value	1.0	2.7
Total Fair Value	2.2	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	9.1	9.3
More than 12 months Fair Value		1.1
Total Fair Value	9.1	10.4
Less than 12 Months Gross Unrealized Losses	0.1	0.2
More than 12 Months Gross Unrealized Losses		0.1
Total Gross Unrealized Losses	0.1	0.3
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.7	11.6
More than 12 months Fair Value	5.6	10.0
Total Fair Value	6.3	21.6
Less than 12 Months Gross Unrealized Losses		0.3
More than 12 Months Gross Unrealized Losses	0.1	1.3
Total Gross Unrealized Losses	0.1	1.6
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	3.4	5.5
More than 12 months Fair Value	0.5	0.2
Total Fair Value	3.9	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	1.4	41.3
More than 12 months Fair Value	13.0	30.0
Total Fair Value	14.4	71.3
Less than 12 Months Gross Unrealized Losses		1.8
More than 12 Months Gross Unrealized Losses	0.2	3.6
Total Gross Unrealized Losses	0.2	5.4
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	15.5	10.5
Total Fair Value	15.5	10.5
Less than 12 Months Gross Unrealized Losses	0.1	0.1
Total Gross Unrealized Losses	$ 0.1	$ 0.1