BENEFIT PLANS (Components of Net Periodic Benefit Cost- Pension Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted-average assumptions used to determine net periodic benefit cost for years ended December 31
Expected return on plan assets	7.00%	7.00%
Pension Benefits [Member]
Components of Net Periodic Benefit Cost
Service cost	$ 5,716	$ 6,715	$ 5,343
Interest cost	35,503	36,230	36,505
Expected return on plan assets	(59,188)	(48,506)	(51,562)
Amortization of prior service cost (credit)	1,340	1,340	(43)
Amortization of actuarial loss	9,826	7,397	6,163
Net periodic benefit cost (credit)	(6,803)	3,176	(3,594)
Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income
Net actuarial loss (gain)	(555)	7,879	33,682
Prior service cost	0	10,868	0
Reclassification of prior service (cost) credit	(1,340)	(1,340)	43
Reclassification of actuarial loss	(9,826)	(7,397)	(6,163)
Amount recognized in other comprehensive income	(11,721)	10,010	27,562
Amount recognized in net periodic pension benefit cost and other comprehensive income	$ (18,524)	$ 13,186	$ 23,968
Weighted-average assumptions used to determine net periodic benefit cost for years ended December 31
Discount rate — PBO	3.72%	4.29%	4.55%
Discount rate — service cost	3.90%	4.63%	4.68%
Discount rate — interest cost	3.35%	3.63%	3.79%
Expected return on plan assets	7.00%	7.00%	7.50%
Weighted-average assumptions used to determine benefit obligation at December 31
Discount rate	4.39%	3.72%	4.29%