CONCENTRATIONS OF CREDIT RISK (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015 counterparty
Concentration Risk [Line Items]
Number of large counterparties for which credit risk is disclosed	5
Energy Producers And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	7.5
Net receivable amount	5.7
Utility Companies And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	15.6
Net receivable amount	14.1
Largest Counterparties
Concentration Risk [Line Items]
Accounts receivable	9.8
Net receivable amount	9.3