Decommissioning Trust Funds (Securities Held) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 5,371.0	$ 4,903.0
Total Unrealized Gains	1,589.0	1,307.0
Total Unrealized Losses	7.0	29.0
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,286.0	3,073.0
Total Unrealized Gains	1,513.0	1,260.0
Total Unrealized Losses	1.0	0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	2,085.0	1,830.0
Total Unrealized Gains	76.0	47.0
Total Unrealized Losses	6.0	29.0
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	769.9	710.9
Total Unrealized Gains	255.1	219.3
Total Unrealized Losses	1.1	5.2
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	487.3	463.3
Total Unrealized Gains	248.9	214.0
Total Unrealized Losses	0	0
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	282.6	247.6
Total Unrealized Gains	6.2	5.3
Total Unrealized Losses	1.1	5.2
Entergy Gulf States Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	637.7	573.7
Total Unrealized Gains	189.5	149.2
Total Unrealized Losses	0.3	3.5
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	395.9	370.8
Total Unrealized Gains	177.6	141.8
Total Unrealized Losses	0	0
Entergy Gulf States Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	241.8	202.9
Total Unrealized Gains	11.9	7.4
Total Unrealized Losses	0.3	3.5
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	383.6	347.3
Total Unrealized Gains	123.6	100.8
Total Unrealized Losses	0.4	1.9
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	239.6	224.2
Total Unrealized Gains	116.7	96.1
Total Unrealized Losses	0	0
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	144.0	123.1
Total Unrealized Gains	6.9	4.7
Total Unrealized Losses	0.4	1.9
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	679.8	603.9
Total Unrealized Gains	193.9	154.3
Total Unrealized Losses	0.3	1.8
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	424.5	380.0
Total Unrealized Gains	188.0	150.8
Total Unrealized Losses	0	0
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	255.3	223.9
Total Unrealized Gains	5.9	3.5
Total Unrealized Losses	$ 0.3	$ 1.8