CONCENTRATIONS OF CREDIT RISK (Details) $ in Millions	6 Months Ended
	Mar. 31, 2016 USD ($) subsegment counterparty
Concentration Risk [Line Items]
Number of groups with potential to affect overall exposure | subsegment	3
Number of large counterparties that are either investment-grate rated or owned by investment-grade rated companies | counterparty	4
Number of large counterparties for which credit risk is disclosed | counterparty	5
Energy Producers And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	$ 9.0
Net receivable amount	5.9
Utility Companies And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	15.1
Net receivable amount	13.3
Largest Counterparties
Concentration Risk [Line Items]
Accounts receivable	13.8
Net receivable amount	$ 10.6