Decommissioning Trust Funds (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Decommissioning Trust Funds [Abstract]
Deferred taxes on unrealized gains/(losses) recorded in OCI for non-regulated decommissioning trusts			$ 217		$ 149
Amortized cost of debt securities	1,612.0		1,612.0		1,530.0
Average coupon rate of debt securities	3.88%		3.88%
Average duration of debt securities, years	5.53		5.53
Average maturity of debt securities, years	8.55		8.55
Proceeds from the dispositions of debt securities	472.0	417.0	1,417.0	1,053.0
Gains from dispositions of debt securities, gross	8.00	12.00	32.00	21.00
Losses from dispositions of debt securities, gross	212.00	3.00	5.00	9.00
Entergy Arkansas [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	205.0		205.0		197.5
Average coupon rate of debt securities	3.35%		3.35%
Average duration of debt securities, years	5.12		5.12
Average maturity of debt securities, years	5.82		5.82
Proceeds from the dispositions of debt securities	15.0	36.5	103.4	82.7
Gains from dispositions of debt securities, gross	0.10	2.20	2.80	3.50
Losses from dispositions of debt securities, gross	0.01	0.10	0.05	0.10
Entergy Gulf States Louisiana [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	169.1		169.1		166.9
Average coupon rate of debt securities	4.68%		4.68%
Average duration of debt securities, years	5.59		5.59
Average maturity of debt securities, years	8.64		8.64
Proceeds from the dispositions of debt securities	35.9	35.9	96.7	56.5
Gains from dispositions of debt securities, gross	3.90	0.80	6.40	1.30
Losses from dispositions of debt securities, gross	0.70	0.40	0.03	0.50
Entergy Louisiana [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	101.6		101.6		91.9
Average coupon rate of debt securities	3.74%		3.74%
Average duration of debt securities, years	5.45		5.45
Average maturity of debt securities, years	9.69		9.69
Proceeds from the dispositions of debt securities	9.5	3.7	19.8	11.5
Gains from dispositions of debt securities, gross	0.10	0	0.20	0.09
Losses from dispositions of debt securities, gross	0.50	0.04	0.03	0.07
System Energy [Member]
Decommissioning Trust Funds [Abstract]
Amortized cost of debt securities	194.3		194.3		175.1
Average coupon rate of debt securities	2.67%		2.67%
Average duration of debt securities, years	4.74		4.74
Average maturity of debt securities, years	6.35		6.35
Proceeds from the dispositions of debt securities	91.8	60.4	315.0	166.9
Gains from dispositions of debt securities, gross	0.50	1.60	3.50	2.10
Losses from dispositions of debt securities, gross	$ 0.05	$ 0.04	$ 0.20	$ 1.00