PENSION AND OTHER POSTRETIREMENT PLANS - Components of net periodic benefit cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net pension expense:
Net (gain) loss	$ (390)	$ 105	$ 409
Pension Benefits
Net pension expense:
Service cost	0	0	0
Interest cost	52	75	87
Expected return on plan assets	(133)	(140)	(137)
Recognized net actuarial (gain) loss	160	171	132
Settlement cost	65	115	0
Net pension expense	144	221	82
Net (gain) loss	(350)	69	353
Amortization of net loss	(160)	(171)	(132)
Total recognized in other comprehensive income (loss)	(510)	(102)	221
Total recognized in net pension expense and other comprehensive income (loss)	(366)	119	303
SERP Benefits
Net pension expense:
Service cost	0	0	0
Interest cost	18	27	37
Expected return on plan assets	(47)	(51)	(55)
Recognized net actuarial (gain) loss	82	80	73
Settlement cost	0	0	0
Net pension expense	53	56	55
Net (gain) loss	(40)	36	56
Amortization of net loss	(82)	(80)	(73)
Total recognized in other comprehensive income (loss)	(122)	(44)	(17)
Total recognized in net pension expense and other comprehensive income (loss)	$ (69)	$ 12	$ 38