PENSION AND POSTRETIREMENT PLANS - Components of Net Periodic Benefit Cost (Credit): (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Benefits
Components of net periodic benefit cost and other amounts recognized in Other Comprehensive Income
Service cost	$ 273	$ 325
Interest cost	225	197
Expected return on plan assets	(608)	(625)
Amortization of net loss	130	83
Amortization of prior service credit	(19)	(19)
Amortization of transition obligation	0	0
Net periodic benefit (credit) cost	1	(39)
SERP Benefits
Components of net periodic benefit cost and other amounts recognized in Other Comprehensive Income
Service cost	65	73
Interest cost	37	32
Expected return on plan assets	0	0
Amortization of net loss	18	30
Amortization of prior service credit	0	0
Amortization of transition obligation	0	1
Net periodic benefit (credit) cost	$ 120	$ 136