PENSION AND POSTRETIREMENT PLANS - Components of Net Periodic Benefit Cost (Credit): (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Pension Benefits
Components of net periodic benefit cost and other amounts recognized in Other Comprehensive Income
Service cost	$ 273	$ 325	$ 818	$ 975
Interest cost	225	198	675	593
Expected return on plan assets	(608)	(626)	(1,823)	(1,876)
Amortization of net loss	130	83	390	248
Amortization of prior service credit	(20)	(20)	(58)	(58)
Amortization of transition obligation	0	0	0	0
Net periodic benefit (credit) cost		(40)	2	(118)
SERP Benefits
Components of net periodic benefit cost and other amounts recognized in Other Comprehensive Income
Service cost	65	73	196	218
Interest cost	37	32	110	95
Expected return on plan assets	0	0	0	0
Amortization of net loss	18	30	53	91
Amortization of prior service credit	0	0	0	0
Amortization of transition obligation	0	1	0	3
Net periodic benefit (credit) cost	$ 120	$ 136	$ 359	$ 407