RETIREMENT PLANS - Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Components of the plan's net periodic pension cost
Projected benefit obligation					$ 15,600
Plan Net Assets					$ 15,600
Pension benefits
Components of the plan's net periodic pension cost
Service cost	$ 54	$ 423	$ 108	$ 846
Interest cost	572	879	1,144	1,758
Expected return on plan assets	(687)	(1,158)	(1,374)	(2,316)
Actuarial (gain)/ loss		(7)		(14)
Net periodic pension expense (benefit)	(61)	137	(122)	274
Company contributions			0	700
Postretirement benefits
Components of the plan's net periodic pension cost
Service cost	35	32	70	64
Interest cost	41	45	82	90
Actuarial (gain)/ loss		(15)		(30)
Net periodic pension expense (benefit)	$ 76	$ 62	$ 152	$ 124