RETIREMENT PLANS - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension benefits
Components of the plan's net periodic pension cost
Service cost	$ 229	$ 439	$ 1,709
Interest cost	2,043	2,585	3,472
Expected return on plan assets	(3,366)	(3,060)	(4,571)
Amortization of actuarial (gain) loss			29
Settlement	34	89	(35)
Net periodic pension cost	(1,060)	53	604
Postretirement benefits
Components of the plan's net periodic pension cost
Service cost	143	139	126
Interest cost	127	163	182
Amortization of actuarial (gain) loss		(11)	(58)
Net periodic pension cost	$ 270	$ 291	$ 250