EMPLOYEE BENEFIT PLANS - Funded status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Supplemental Benefit Plan
Change in benefit obligations
Benefit obligations at beginning of period	$ 338	$ 381
Interest cost	16	7	$ 4
Actuarial (gain) loss	4	(50)
Benefit obligations at end of period	358	338	381
Change in plan assets
Funded status at period end	(358)	(338)
Accumulated benefit obligation	358	338
Postretirement Health Benefit Plan
Change in benefit obligations
Benefit obligations at beginning of period	12,534	16,992
Service cost	78	156	192
Interest cost	599	441	427
Actuarial (gain) loss	1,137	(4,392)
Benefits paid	(680)	(663)
Benefit obligations at end of period	13,668	12,534	$ 16,992
Change in plan assets
Employer contributions	680	663
Benefits paid	(680)	(663)
Funded status at period end	(13,668)	(12,534)
Accumulated benefit obligation	$ 13,668	$ 12,534