PENSION AND OTHER POSTRETIREMENT BENEFITS - Schedule of Defined Benefit Plans Disclosure (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 974	$ 1,387	$ 4,349	$ 4,187
Interest Cost	3,862	4,307	11,388	12,971
Expected Return on Plan Assets	(5,569)	(5,077)	(16,473)	(15,213)
Amortizations:
Prior Service Cost	26	26	79	79
Actuarial Loss	2,647	2,398	8,077	7,195
Net Periodic Benefit Cost	1,940	3,041	7,420	9,219
Capitalized Benefit Cost	(410)	(454)	(1,470)	(1,423)
Deferred Benefit Cost	(377)	(516)	(1,193)	(1,710)
Total Net Periodic Benefit Expense	1,153	2,071	4,757	6,086
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	182	129	511	400
Interest Cost	560	729	1,775	2,163
Expected Return on Plan Assets	(1,345)	(1,147)	(4,036)	(3,428)
Amortizations:
Prior Service Cost	(180)	(144)	(468)	(432)
Actuarial Loss	255	292	640	876
Net Periodic Benefit Cost	(528)	(141)	(1,578)	(421)
Capitalized Benefit Cost	57	(115)	(157)	(270)
Deferred Benefit Cost	(90)	118	701	352
Total Net Periodic Benefit Expense	$ (561)	$ (138)	$ (1,034)	$ (339)