BENEFIT PLANS (Components of Net Periodic Benefit Cost- Other Postretirement Benefits) (Details) - Postretirement Benefits [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of Net Periodic Benefit Cost
Service cost	$ 1,357	$ 1,167	$ 1,123
Service cost	1,358
Interest cost	1,240	1,260	1,209
Amortization of prior service credit	(3,962)	(4,236)	(4,236)
Amortization of actuarial gain	(1,298)	(1,587)	(1,751)
Net periodic benefit cost (credit)	(2,662)	(3,396)	(3,655)
Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income
Net actuarial loss (gain)	835	342	(111)
Reclassification of prior service credit	3,962	4,236	4,236
Reclassification of actuarial gain	1,298	1,587	1,751
Amount recognized in other comprehensive income	6,095	6,165	5,876
Amount recognized in net periodic pension benefit cost and other comprehensive income	$ 3,433	$ 2,769	$ 2,221
Weighted-average assumptions used to determine net periodic benefit cost for years ended December 31
Discount rate — PBO	3.34%	3.59%	3.69%
Discount rate — service cost	3.56%	3.96%	3.77%
Discount rate — interest cost	2.90%	2.89%	2.81%
Weighted-average assumptions used to determine benefit obligation at December 31
Discount rate	4.01%	3.33%	3.58%