CONCENTRATIONS OF CREDIT RISK (Details) $ in Millions	3 Months Ended
	Dec. 31, 2015 USD ($) subsegment counterparty
Concentration Risk [Line Items]
Number of groups with potential to affect overall exposure | subsegment	3
Number of large counterparties for which credit risk is disclosed | counterparty	5
Energy Producers And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	$ 11.2
Net receivable amount	5.3
Utility Companies And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	25.3
Net receivable amount	22.2
Largest Counterparties
Concentration Risk [Line Items]
Accounts receivable	16.3
Net receivable amount	$ 12.9