CONCENTRATIONS OF CREDIT RISK (Details) $ in Millions	9 Months Ended
	Jun. 30, 2016 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	$ 10.1
Net receivable amount	6.5
Utility Companies And Their Affiliates
Concentration Risk [Line Items]
Accounts receivable	40.9
Net receivable amount	39.0
Largest Counterparties
Concentration Risk [Line Items]
Accounts receivable	20.6
Net receivable amount	$ 19.5