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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Municipal Franchise Taxes      
Municipal franchise taxes $ 11.8ede_PublicUtilityMunicipalFranchiseTaxes $ 11.2ede_PublicUtilityMunicipalFranchiseTaxes $ 10.4ede_PublicUtilityMunicipalFranchiseTaxes
Property, Plant and Equipment      
Period for refund of pro rata amount of the original cost of the extension to developers 5 years    
Liability for refund of pro rata amount of the original cost of the extension to developers $ 1.9ede_LiabilityForRefundOfProRataAmountOfOriginalCostOfExtensionToDevelopers $ 4.2ede_LiabilityForRefundOfProRataAmountOfOriginalCostOfExtensionToDevelopers