BENEFIT PLANS (Components of Net Periodic Benefit Cost- Other Postretirement Benefits) (Details) - Other Postretirement Benefit Plans, Defined Benefit [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components of Net Periodic Benefit Cost
Service cost	$ 1,520	$ 1,317	$ 1,358
Service cost	1,521	1,317
Interest cost	969	1,388	1,240
Amortization of prior service credit	(3,919)	(3,919)	(3,962)
Amortization of actuarial gain	(806)	(1,309)	(1,298)
Net periodic benefit cost (credit)	(2,235)	(2,523)	(2,662)
Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income
Net actuarial loss (gain)	(5,168)	2,673	835
Reclassification of prior service credit	3,919	3,919	3,962
Reclassification of actuarial gain	806	1,309	1,298
Amount recognized in other comprehensive income	(443)	7,901	6,095
Amount recognized in net periodic pension benefit cost and other comprehensive income	$ (2,678)	$ 5,378	$ 3,433
Weighted-average assumptions used to determine net periodic benefit cost for years ended December 31
Discount rate — PBO	2.84%	4.01%	3.34%
Discount rate — service cost	3.09%	4.23%	3.56%
Discount rate — interest cost	2.42%	3.63%	2.90%
Weighted-average assumptions used to determine benefit obligation at December 31
Discount rate	2.09%	2.84%	4.01%