COMPREHENSIVE INCOME - Changes in accumulated other comprehensive loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
COMPREHENSIVE INCOME
Foreign Currency Translation Adjustments, Beginning balance	$ (8,596)	$ (6,783)
Foreign Currency Translation Adjustments, Other comprehensive income (loss) before reclassifications	642	(1,813)
Foreign Currency Translation Adjustments, Net current period other comprehensive (loss) income	642	(1,813)
Foreign Currency Translation Adjustments, Ending balance	(7,954)	(8,596)
Defined Benefit Pension Items, Beginning balance	(11,597)	(18,011)
Defined Benefit Pension Items, Other comprehensive (loss) income before reclassifications	1,874	5,767
Defined Benefit Pension Items, Amounts reclassified from accumulated other comprehensive loss	366	647
Defined Benefit Pension Items, Net current period other comprehensive (loss) income	2,240	6,414
Defined Benefit Pension Items, Ending balance	(9,357)	(11,597)
Beginning balance	(20,193)	(24,794)
Other comprehensive loss before reclassifications	2,516	3,954
Amounts reclassified from accumulated other comprehensive loss	366	647
Net current period other comprehensive income	2,882	4,601
Ending balance	$ (17,311)	$ (20,193)