PENSION AND OTHER POSTRETIREMENT BENEFITS - Schedule of Defined Benefit Plans Disclosure (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 1,688	$ 1,081	$ 3,375	$ 2,800
Interest Cost	3,763	4,435	7,526	8,664
Expected Return on Plan Assets	(5,452)	(4,942)	(10,904)	(10,135)
Amortizations:
Prior Service Cost	26	27	53	53
Actuarial Loss	2,715	2,360	5,430	4,797
Net Periodic Benefit Cost	2,740	2,961	5,480	6,179
Capitalized Benefit Cost	(517)	(374)	(1,061)	(968)
Deferred Benefit Cost	(408)	(653)	(816)	(1,194)
Total Net Periodic Benefit Expense	1,815	1,934	3,603	4,017
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	165	37	329	271
Interest Cost	608	806	1,216	1,434
Expected Return on Plan Assets	(1,346)	(1,133)	(2,691)	(2,282)
Amortizations:
Prior Service Cost	(144)	(145)	(288)	(288)
Actuarial Loss	193	321	385	584
Net Periodic Benefit Cost	(524)	(114)	(1,049)	(281)
Capitalized Benefit Cost	(106)	(99)	(214)	(155)
Deferred Benefit Cost	396	119	792	235
Total Net Periodic Benefit Expense	$ (234)	$ (94)	$ (471)	$ (201)