Decommissioning Trust Funds (Securities Held) (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 4,176,000,000	$ 3,788,000,000
Total Unrealized Gains	799,000,000	538,000,000
Total Unrealized Losses	6,000,000	19,000,000
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	2,453,000,000	2,129,000,000
Total Unrealized Gains	673,000,000	423,000,000
Total Unrealized Losses	2,000,000	14,000,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,723,000,000	1,659,000,000
Total Unrealized Gains	126,000,000	115,000,000
Total Unrealized Losses	4,000,000	5,000,000
Entergy Arkansas [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	599,900,000	541,700,000
Total Unrealized Gains	133,400,000	86,100,000
Total Unrealized Losses	100,000	800,000
Entergy Arkansas [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	378,800,000	329,400,000
Total Unrealized Gains	117,200,000	70,900,000
Total Unrealized Losses		400,000
Entergy Arkansas [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	221,100,000	212,300,000
Total Unrealized Gains	16,200,000	15,200,000
Total Unrealized Losses	100,000	400,000
Entergy Gulf States Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	475,000,000	420,900,000
Total Unrealized Gains	88,200,000	56,100,000
Total Unrealized Losses		1,100,000
Entergy Gulf States Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	289,400,000	238,700,000
Total Unrealized Gains	71,400,000	40,900,000
Total Unrealized Losses		800,000
Entergy Gulf States Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	185,600,000	182,200,000
Total Unrealized Gains	16,800,000	15,200,000
Total Unrealized Losses		300,000
Entergy Louisiana [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	285,500,000	254,000,000
Total Unrealized Gains	59,400,000	38,500,000
Total Unrealized Losses	100,000	1,800,000
Entergy Louisiana [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	174,000,000	149,200,000
Total Unrealized Gains	49,300,000	29,700,000
Total Unrealized Losses		1,600,000
Entergy Louisiana [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	111,500,000	104,800,000
Total Unrealized Gains	10,100,000	8,800,000
Total Unrealized Losses	100,000	200,000
System Energy [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	484,200,000	423,400,000
Total Unrealized Gains	74,400,000	44,900,000
Total Unrealized Losses	100,000	5,500,000
System Energy [Member] | Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	280,000,000	237,200,000
Total Unrealized Gains	64,500,000	35,400,000
Total Unrealized Losses	100,000	5,400,000
System Energy [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	204,200,000	186,200,000
Total Unrealized Gains	9,900,000	9,500,000
Total Unrealized Losses		$ 100,000