EMPLOYEE BENEFIT PLANS (Details) - USD ($)	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Components of net periodic cost
Discretionary contribution	$ 0	$ 0
Pension
Components of net periodic cost
Service cost	2,056,000	1,845,000
Interest cost	2,647,000	3,043,000
Expected return on plan assets	(5,057,000)	(4,763,000)
Recognized actuarial loss	2,746,000	1,441,000
Prior service cost amortization	25,000	25,000
Net periodic benefit cost	2,417,000	1,591,000
OPEB
Components of net periodic cost
Service cost	1,355,000	1,101,000
Interest cost	2,004,000	2,081,000
Expected return on plan assets	(1,560,000)	(1,379,000)
Recognized actuarial loss	2,791,000	1,617,000
Prior service cost amortization	(49,000)	(91,000)
Net periodic benefit cost	4,541,000	$ 3,329,000
Maximum | OPEB
Components of net periodic cost
Estimated contributions over next five years	10,000,000
Minimum | OPEB
Components of net periodic cost
Estimated contributions over next five years	$ 5,000,000