RETIREMENT PLANS - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Components of the plan's net periodic pension cost
Company contributions	$ 0	$ 0
Pension Plans
Components of the plan's net periodic pension cost
Service cost	423	447
Interest cost	879	841
Expected return on plan assets	(1,158)	(1,263)
Actuarial gain/ loss	(7)	7
Net periodic pension expense	137	32
Funded status of plan
Plan Net Assets			$ 15,600
Projected benefit obligation			$ 15,100
Postretirement Benefits
Components of the plan's net periodic pension cost
Service cost	32	37
Interest cost	45	40
Actuarial gain/ loss	(15)	(17)
Net periodic pension expense	$ 62	$ 60