Asset Retirement Obligations (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Jun. 30, 2012 Entergy Louisiana [Member]	Mar. 31, 2011 System Energy [Member]	Jun. 30, 2012 Entergy Wholesale Commodities [Member]	Dec. 31, 2011 Entergy Wholesale Commodities [Member]
Reduction in decommissioning liability			$ 38.9	$ 60.6	$ 34.1
Decommissioning expense				49.0	34.1
Increase in decommissioning liability		48.9
Present value of the difference between the stipulated contract amount for decommissioning the plants less the decommissioning cost	$ 546.5