Asset Retirement Obligations (Entergy Corporation, Entergy Arkansas, Entergy Gulf States Louisiana, Entergy Louisiana, Entergy Mississippi, Entergy New Orleans, Entergy Texas, and System Energy) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Entergy Gulf States Louisiana [Member]
Difference between estimated incurred removal costs and estimated removal costs recovered in rates
Regulatory Liabilities	$ (30.3)	$ (24.9)
Entergy Louisiana [Member]
Difference between estimated incurred removal costs and estimated removal costs recovered in rates
Regulatory Liabilities	(62.6)	(52.9)
System Energy [Member] | Asset Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	11.8	12.2
Entergy Mississippi [Member] | Asset Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	48.5	46.1
Entergy New Orleans [Member] | Asset Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	16.3	15.4
Entergy Texas [Member] | Asset Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	4.5	7.3
Asset Retirement Obligation [Member] | Entergy Arkansas
Difference between estimated incurred removal costs and estimated removal costs recovered in rates
Regulatory Liabilities	$ (16.4)	$ (24.0)