PENSION AND POSTRETIREMENT PLANS - Components of Net Periodic Benefit Cost (Credit): (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits
Components of net periodic benefit (credit) cost and other amounts recognized in other comprehensive income:
Service cost	$ 265	$ 273
Interest cost	193	225
Expected return on plan assets	(713)	(608)
Amortization of net loss	100	130
Amortization of prior service credit	(19)	(19)
Net periodic benefit (credit) cost	(174)	1
SERP Benefits
Components of net periodic benefit (credit) cost and other amounts recognized in other comprehensive income:
Service cost	93	65
Interest cost	37	37
Expected return on plan assets	0	0
Amortization of net loss	57	18
Amortization of prior service credit	0	0
Net periodic benefit (credit) cost	$ 187	$ 120