Decommissioning Trust Funds (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Gross Unrealized Losses	$ 0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	9.0	0
More than 12 months Fair Value	0	0
Total Fair Value	9.0	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	277.0	892.0
More than 12 months Fair Value	163.0	60.0
Total Fair Value	440.0	952.0
Less than 12 months Gross Unrealized Losses	2.0	24.0
More than 12 months Gross Unrealized Losses	4.0	5.0
Total Gross Unrealized Losses	6.0	29.0
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.1	0
More than 12 months Fair Value	0	0
Total Fair Value	0.1	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	56.5	153.2
More than 12 months Fair Value	34.8	6.9
Total Fair Value	91.3	160.1
Less than 12 months Gross Unrealized Losses	0.3	4.8
More than 12 months Gross Unrealized Losses	0.8	0.4
Total Gross Unrealized Losses	1.1	5.2
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.1	0
More than 12 months Fair Value	0	0
Total Fair Value	0.1	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	14.0	91.9
More than 12 months Fair Value	15.0	4.6
Total Fair Value	29.0	96.5
Less than 12 months Gross Unrealized Losses	0.1	3.1
More than 12 months Gross Unrealized Losses	0.2	0.4
Total Gross Unrealized Losses	0.3	3.5
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.1	0
More than 12 months Fair Value	0	0
Total Fair Value	0.1	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	19.1	38.3
More than 12 months Fair Value	12.1	1.7
Total Fair Value	31.2	40.0
Less than 12 months Gross Unrealized Losses	0.1	1.7
More than 12 months Gross Unrealized Losses	0.3	0.2
Total Gross Unrealized Losses	0.4	1.9
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months Fair Value	0.1	0
More than 12 months Fair Value	0	0
Total Fair Value	0.1	0
Less than 12 months Gross Unrealized Losses		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	51.6	121.7
More than 12 months Fair Value	6.5	0.9
Total Fair Value	58.1	122.6
Less than 12 months Gross Unrealized Losses	0.2	1.7
More than 12 months Gross Unrealized Losses	0.1	0.1
Total Gross Unrealized Losses	$ 0.3	$ 1.8