Decommissioning Trust Funds (Securities Held) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 2,735.0	$ 2,459.0
Total Unrealized Gains	929.0	662.0
Total Unrealized Losses	1.0	1.0
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,732.0	1,731.0
Total Unrealized Gains	63.0	116.0
Total Unrealized Losses	25.0	5.0
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	410.3	384.0
Total Unrealized Gains	158.8	116.1
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	236.2	216.6
Total Unrealized Gains	6.9	14.5
Total Unrealized Losses	4.0	0.2
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	327.9	288.5
Total Unrealized Gains	101.5	69.8
Total Unrealized Losses	0.4
Entergy Gulf States Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	188.1	188.9
Total Unrealized Gains	9.0	15.8
Total Unrealized Losses	2.4	0.1
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	199.7	175.5
Total Unrealized Gains	71.2	48.9
Total Unrealized Losses		0.1
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	112.0	111.9
Total Unrealized Gains	5.9	9.4
Total Unrealized Losses	1.3	0.1
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	324.1	283.6
Total Unrealized Gains	99.9	63.6
Total Unrealized Losses		0.2
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	213.5	207.0
Total Unrealized Gains	4.6	9.3
Total Unrealized Losses	$ 1.8	$ 0.1