CONCENTRATIONS OF CREDIT RISK (Details) - Jun. 30, 2015 $ in Millions	USD ($) counterparty
Concentration Risk [Line Items]
Number of large counterparties for which credit risk is disclosed | counterparty	5
Energy Producers And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	$ 11.3
Net receivable amount	8.6
Utility Companies And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	17.6
Net receivable amount	15.5
Largest Counterparties
Concentration Risk [Line Items]
Accounts receivable	17.2
Net receivable amount	$ 14.9