EMPLOYEE BENEFIT PLANS - Funded status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Nonunion Defined Benefit Pension Plan
Change in benefit obligations
Interest cost			$ 624
Supplemental Benefit Plan
Change in benefit obligations
Benefit obligations at beginning of period	$ 392	$ 3,236
Interest cost	4	9	39
Actuarial (gain) loss	(15)	34
Benefits paid		(2,887)
Benefit obligations at end of period	381	392	3,236
Change in plan assets
Employer contributions		2,887
Benefits paid		(2,887)
Funded status at period end	(381)	(392)
Accumulated benefit obligation	381	392
Postretirement Health Benefit Plan
Change in benefit obligations
Benefit obligations at beginning of period	18,751	20,630
Service cost	192	187	320
Interest cost	427	576	1,212
Actuarial (gain) loss	(1,736)	(2,027)
Benefits paid	(642)	(615)
Benefit obligations at end of period	16,992	18,751	$ 20,630
Change in plan assets
Employer contributions	642	615
Benefits paid	(642)	(615)
Funded status at period end	(16,992)	(18,751)
Accumulated benefit obligation	$ 16,992	$ 18,751