RETIREMENT PLANS - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Components of the plan's net periodic pension cost
Projected benefit obligation			$ 15,600
Plan Net Assets			$ 15,600
Pension Plans
Components of the plan's net periodic pension cost
Service cost	$ 54	$ 423
Interest cost	572	879
Expected return on plan assets	(687)	(1,158)
Actuarial (gain)/ loss		(7)
Net periodic pension expense (benefit)	(61)	137
Postretirement Benefits
Components of the plan's net periodic pension cost
Service cost	35	32
Interest cost	41	45
Actuarial (gain)/ loss		(15)
Net periodic pension expense (benefit)	$ 76	$ 62