RETIREMENT PLANS (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			6 Months Ended
	Dec. 31, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Retirement plans
Curtailment gain, net of taxes of $0		$ 0		$ 0	$ 1,699	$ 0
Other disclosures
Net actuarial gains arising during the period		0		0	880	0
Reduction in unrecognized benefit costs previously included in AOCI		(20)		(16)	(80)	(33)
Pension Plan
Net periodic benefit cost:
Service cost		0		50	50	100
Interest cost		72		94	155	187
Expected return on plan assets		(172)		(160)	(335)	(321)
Amortization of prior service cost (credit)		0		2	1	3
Amortization of net actuarial loss		0		1	35	4
Curtailment cost (income)					53	0
Net periodic benefit (income) cost		(100)		(13)	(41)	(27)
Other disclosures
Estimated future Pension Plan contributions		0			0
SERP
Net periodic benefit cost:
Service cost		0		9	3	18
Interest cost		15		21	33	42
Amortization of prior service cost (credit)		0		(1)	(1)	(2)
Amortization of net actuarial loss		0		1	5	2
Curtailment cost (income)					(53)	0
Net periodic benefit (income) cost		15		30	(13)	60
Postretirement Medical
Net periodic benefit cost:
Service cost		0		0	0	0
Interest cost		20		25	40	50
Amortization of prior service cost (credit)		0		0	0	0
Amortization of net actuarial loss		20		13	40	26
Curtailment cost (income)					0	0
Net periodic benefit (income) cost		$ 40		$ 38	$ 80	$ 76
Pension Plan And SERP
Retirement plans
Curtailment gain, net of taxes of $0	$ 1,699
Other disclosures
Net actuarial gains arising during the period			$ 880
Reduction in unrecognized benefit costs previously included in AOCI	$ 1,699