RETIREMENT PLANS - Schedule of post-retirement health benefit expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure
Service cost	$ 1,190	$ 1,355	$ 1,300
Interest cost	2,826	2,632	3,116
Recognized actuarial loss	(21,350)	(2,943)
Net periodic pension cost	365	1,346	2,186
Net loss (gain) during the period	(5,323)	(5,883)	3,188
Amortization of prior service cost		(1)	(1)
Total recognized in other comprehensive income (loss)	(6,582)	(7,956)	1,220
Total recognized net periodic pension cost and other comprehensive income	(6,217)	(6,610)	3,406
Postretirement Health Coverage
Defined Benefit Plan Disclosure
Service cost	34	43	38
Interest cost	111	103	125
Amortization of transition obligation	0	0	0
Net periodic pension cost	145	146	163
Net loss (gain) during the period	(758)	(53)	238
Amortization of prior service cost	0	0	0
Total recognized in other comprehensive income (loss)	(758)	(53)	238
Total recognized net periodic pension cost and other comprehensive income	$ (613)	$ 93	$ 401