SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, PENSION AND POSTEMPLOYMENT PLANS (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2016 USD ($) plan	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of noncontributory defined benefit retirement plans (in plans) | plan		2
Employer contributions | $	$ 30,000		$ 0
Number of noncontributory medical and life insurance plans (in plans) | plan		2
OPEB
Defined Benefit Plan Disclosure [Line Items]
Employer contributions | $		$ 3,235	$ 5,672	$ 5,000