Decommissioning Trust Funds (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Decommissioning Trust Funds [Abstract]
Deferred taxes on unrealized gains/(losses) recorded in OCI for non-regulated decommissioning trusts	$ 265,000,000		$ 211,000,000
Amortized cost of debt securities	1,654,000,000		1,637,000,000
Average coupon rate of debt securities	3.71%
Average duration of debt securities, years	5 years 3 months 9 days
Average maturity of debt securities, years	8 years 0 months 29 days
Proceeds from the dispositions of debt securities	398,000,000	536,000,000
Gains from dispositions of debt securities, gross	6,000,000	12,000,000
Losses from dispositions of debt securities, gross	2,000,000	2,000,000
Entergy Arkansas [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	211,700,000		202,300,000
Average coupon rate of debt securities	3.12%
Average duration of debt securities, years	5 years 0 months 22 days
Average maturity of debt securities, years	5 years 9 months 30 days
Proceeds from the dispositions of debt securities	56,100,000	54,700,000
Gains from dispositions of debt securities, gross	1,400,000	2,000,000
Losses from dispositions of debt securities, gross	100,000
Entergy Gulf States Louisiana [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	175,200,000		174,100,000
Average coupon rate of debt securities	4.60%
Average duration of debt securities, years	5 years 5 months 21 days
Average maturity of debt securities, years	8 years 4 months 11 days
Proceeds from the dispositions of debt securities	23,300,000	38,100,000
Gains from dispositions of debt securities, gross	1,100,000	1,500,000
Losses from dispositions of debt securities, gross	1,700	5,500
Entergy Louisiana [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	104,500,000		102,600,000
Average coupon rate of debt securities	3.57%
Average duration of debt securities, years	5 years 2 months 18 days
Average maturity of debt securities, years	9 years 2 months 7 days
Proceeds from the dispositions of debt securities	3,600,000	6,800,000
Gains from dispositions of debt securities, gross	40,000	30,000
Losses from dispositions of debt securities, gross	10,000	2,800
System Energy [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	203,300,000		197,800,000
Average coupon rate of debt securities	2.75%
Average duration of debt securities, years	4 years 7 months 3 days
Average maturity of debt securities, years	6 years 2 months 18 days
Proceeds from the dispositions of debt securities	25,600,000	125,400,000
Gains from dispositions of debt securities, gross	20,000	1,200,000
Losses from dispositions of debt securities, gross	$ 70,000	$ 100,000