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, 2014	Dec. 31, 2013
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	$ 23.0	$ 0
More than 12 months Fair Value	0	0
Total Fair Value	23.0	0
Less than 12 Months Gross Unrealized Losses	1.0	0
More than 12 Months Gross Unrealized Losses	0	0
Total Gross Unrealized Losses	1.0	0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	427.0	892.0
More than 12 months Fair Value	211.0	60.0
Total Fair Value	638.0	952.0
Less than 12 Months Gross Unrealized Losses	3.0	24.0
More than 12 Months Gross Unrealized Losses	7.0	5.0
Total Gross Unrealized Losses	10.0	29.0
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	4.5	0
More than 12 months Fair Value	0	0
Total Fair Value	4.5	0
Less than 12 Months Gross Unrealized Losses	0	0
More than 12 Months Gross Unrealized Losses	0	0
Total Gross Unrealized Losses	0	0
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	94.5	153.2
More than 12 months Fair Value	52.0	6.9
Total Fair Value	146.5	160.1
Less than 12 Months Gross Unrealized Losses	0.6	4.8
More than 12 Months Gross Unrealized Losses	1.5	0.4
Total Gross Unrealized Losses	2.1	5.2
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.6	0
More than 12 months Fair Value	0	0
Total Fair Value	0.6	0
Less than 12 Months Gross Unrealized Losses	0	0
More than 12 Months Gross Unrealized Losses	0	0
Total Gross Unrealized Losses	0	0
Entergy Gulf States Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	16.7	91.9
More than 12 months Fair Value	21.8	4.6
Total Fair Value	38.5	96.5
Less than 12 Months Gross Unrealized Losses	0.1	3.1
More than 12 Months Gross Unrealized Losses	0.6	0.4
Total Gross Unrealized Losses	0.7	3.5
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.4	0
More than 12 months Fair Value	0	0
Total Fair Value	0.4	0
Less than 12 Months Gross Unrealized Losses	0	0
More than 12 Months Gross Unrealized Losses	0	0
Total Gross Unrealized Losses	0	0
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	25.0	38.3
More than 12 months Fair Value	17.4	1.7
Total Fair Value	42.4	40.0
Less than 12 Months Gross Unrealized Losses	0.1	1.7
More than 12 Months Gross Unrealized Losses	0.6	0.2
Total Gross Unrealized Losses	0.7	1.9
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.9	0
More than 12 months Fair Value	0	0
Total Fair Value	0.9	0
Less than 12 Months Gross Unrealized Losses	0	0
More than 12 Months Gross Unrealized Losses	0	0
Total Gross Unrealized Losses	0	0
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	92.2	121.7
More than 12 months Fair Value	7.8	0.9
Total Fair Value	100.0	122.6
Less than 12 Months Gross Unrealized Losses	0.4	1.7
More than 12 Months Gross Unrealized Losses	0.2	0.1
Total Gross Unrealized Losses	$ 0.6	$ 1.8