Decommissioning Trust Funds (Securities Held) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 2,888.0	$ 2,459.0
Total Unrealized Gains	1,067.0	662.0
Total Unrealized Losses	1.0	1.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,740.0	1,731.0
Total Unrealized Gains	59.0	116.0
Total Unrealized Losses	24.0	5.0
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	430.8	384.0
Total Unrealized Gains	181.7	116.1
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	239.0	216.6
Total Unrealized Gains	6.3	14.5
Total Unrealized Losses	4.1	0.2
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	347.2	288.5
Total Unrealized Gains	118.0	69.8
Entergy Gulf States Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	190.4	188.9
Total Unrealized Gains	8.7	15.8
Total Unrealized Losses	2.6	0.1
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	214.7	175.5
Total Unrealized Gains	82.5	48.9
Total Unrealized Losses		0.1
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	110.7	111.9
Total Unrealized Gains	5.6	9.4
Total Unrealized Losses	1.5	0.1
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	343.8	283.6
Total Unrealized Gains	117.9	63.6
Total Unrealized Losses		0.2
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	219.6	207.0
Total Unrealized Gains	4.6	9.3
Total Unrealized Losses	$ 1.2	$ 0.1