EMPLOYEE BENEFIT PLANS (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Components of net periodic cost
Discretionary contribution			$ 0
Pension
Components of net periodic cost
Service cost	$ 2,034,000	$ 2,087,000	4,069,000	$ 4,174,000
Interest cost	2,624,000	2,442,000	5,247,000	4,885,000
Expected return on plan assets	(4,909,000)	(4,828,000)	(9,819,000)	(9,656,000)
Recognized actuarial loss	1,885,000	2,206,000	3,769,000	4,413,000
Prior service cost amortization	26,000	28,000	53,000	55,000
Net periodic benefit cost	1,660,000	1,935,000	3,319,000	3,871,000
OPEB
Components of net periodic cost
Service cost	1,151,000	1,095,000	2,303,000	2,190,000
Interest cost	1,591,000	1,387,000	3,182,000	2,773,000
Expected return on plan assets	(1,338,000)	(1,191,000)	(2,676,000)	(2,383,000)
Recognized actuarial loss	1,165,000	1,092,000	2,330,000	2,185,000
Prior service cost amortization	(91,000)	(91,000)	(182,000)	(182,000)
Net periodic benefit cost	$ 2,478,000	$ 2,292,000	$ 4,957,000	$ 4,583,000