PENSION AND POSTRETIREMENT PLANS - Components of Net Periodic Benefit Cost (Credit): (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Benefits
Components of net periodic benefit cost and other amounts recognized in Other Comprehensive Income
Service cost	$ 272	$ 325	$ 545	$ 650
Interest cost	225	198	450	395
Expected return on plan assets	(607)	(625)	(1,215)	(1,250)
Amortization of net loss	130	82	260	165
Amortization of prior service credit	(19)	(19)	(38)	(38)
Amortization of transition obligation	0	0	0	0
Net periodic benefit (credit) cost	1	(39)	2	(78)
SERP Benefits
Components of net periodic benefit cost and other amounts recognized in Other Comprehensive Income
Service cost	66	72	131	145
Interest cost	36	31	73	63
Expected return on plan assets	0	0	0	0
Amortization of net loss	17	31	35	61
Amortization of prior service credit	0	0	0	0
Amortization of transition obligation	0	1	0	2
Net periodic benefit (credit) cost	$ 119	$ 135	$ 239	$ 271