BENEFIT PLANS (Components of Net Periodic Benefit Cost- Pension Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted-average assumptions used to determine net periodic benefit cost for years ended December 31
Expected return on plan assets	5.75%	7.00%
Pension Plans, Defined Benefit [Member]
Components of Net Periodic Benefit Cost
Service cost	$ 4,995	$ 5,716	$ 6,715
Interest cost	37,640	35,503	36,230
Expected return on plan assets	(47,751)	(59,188)	(48,506)
Amortization of prior service cost	1,340	1,340	1,340
Amortization of actuarial loss	5,433	9,826	7,397
Net periodic benefit cost (credit)	1,657	(6,803)	3,176
Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income
Net actuarial loss (gain)	33,717	(555)	7,879
Prior service cost	0	0	10,868
Reclassification of prior service (cost) credit	(1,340)	(1,340)	(1,340)
Reclassification of actuarial loss	(5,433)	(9,826)	(7,397)
Amount recognized in other comprehensive income	26,944	(11,721)	10,010
Amount recognized in net periodic pension benefit cost and other comprehensive income	$ 28,601	$ (18,524)	$ 13,186
Weighted-average assumptions used to determine net periodic benefit cost for years ended December 31
Discount rate — PBO	4.39%	3.72%	4.29%
Discount rate — service cost	4.59%	3.90%	4.63%
Discount rate — interest cost	4.02%	3.35%	3.63%
Expected return on plan assets	5.75%	7.00%	7.00%
Weighted-average assumptions used to determine benefit obligation at December 31
Discount rate	3.28%	4.39%	3.72%