Summary Of Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended																									1 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2012 MW	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Entergy Gulf States Louisiana [Member]	Dec. 31, 2011 Entergy Gulf States Louisiana [Member]	Dec. 31, 2010 Entergy Gulf States Louisiana [Member]	Dec. 31, 2012 Entergy Louisiana [Member]	Dec. 31, 2011 Entergy Louisiana [Member]	Dec. 31, 2010 Entergy Louisiana [Member]	Dec. 31, 2012 Entergy Texas [Member]	Dec. 31, 2011 Entergy Texas [Member]	Dec. 31, 2010 Entergy Texas [Member]	Dec. 31, 2012 Entergy Arkansas [Member]	Dec. 31, 2011 Entergy Arkansas [Member]	Dec. 31, 2010 Entergy Arkansas [Member]	Dec. 31, 2012 Entergy Mississippi [Member]	Dec. 31, 2011 Entergy Mississippi [Member]	Dec. 31, 2010 Entergy Mississippi [Member]	Dec. 31, 2012 Entergy New Orleans [Member]	Dec. 31, 2011 Entergy New Orleans [Member]	Dec. 31, 2010 Entergy New Orleans [Member]	Dec. 31, 2012 System Energy [Member]	Dec. 31, 2011 System Energy [Member]	Dec. 31, 2010 System Energy [Member]	Dec. 31, 2012 Entergy Wholesale Commodities [Member] item	Mar. 31, 2011 Vermont Yankee [Member]	Dec. 31, 2012 Vermont Yankee [Member]
Estimate of uprate for recovered performance		178
Estimate of rerate for receovered performance		55
Depreciation rates on average depreciable property		2.50%	2.60%	2.60%	1.80%	1.80%	1.80%	2.40%	2.50%	2.40%	2.40%	2.20%	2.30%	2.50%	2.60%	2.90%	2.60%	2.60%	2.60%	3.00%	3.00%	3.10%	2.80%	2.80%	2.90%
Depreciation rates on average depreciable utility property		2.40%	2.50%	2.50%
Depreciatiopn rates on average depreciable non-utility property			3.90%	3.70%
Accumulated depreciation of non-utility property		$ 230.4	$ 214.3		$ 142.0	$ 136.0		$ 2.8	$ 2.7		$ 10.0	$ 9.8
Construction expenditures in accounts payable		267.0	171.0		9.7	13.7		110.4	27.0		8.6	4.3		56.3	14.1		4.8	4.3		1.9	3.6		13.5	32.9
Options outstanding excluded from the calculation of diluted earnings per share		7,164,319	5,712,604	5,380,262
Stock-based compensation plans award vesting period		3 years
Percentage of interest in River Bend by Entergy Gulf States Louisiana					30.00%
Portion of percentage of interest of River Bend plant costs, generation, revenues and expenses operating the Louisiana retail deregulated portion of River Bend		15.00%
Rate at which electricity sold to retail customers					0.046
Limit above which incremental revenue shared between ratepayers and shareholders		0.046
Number of nuclear power plants pending for NRC license renewals																										2
Period of renewal of operating license by NRC																											20 years
Lease Expiration Date																												Mar. 01, 2032
Estimated fair value of nuclear plant	162.0
Carrying value of nuclear plant	517.5
Asset impairment charges	355.5	355.5
After tax asset impairment charge	$ 223.5	$ 223.5