COMPONENTS OF PENSION AND OTHER POST-EMPLOYMENT BENEFIT (OPEB) PLANS NET PERIODIC BENEFIT COSTS - Schedule of Components of Net Periodic Benefit (Credit) Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 296	$ 987
Interest Cost	5,044	6,275
Expected Return on Plan Assets	(10,455)	(10,114)
Amortization of Prior Service Credits	0	(92)
Amortization of Actuarial Loss	1,730	1,490
Net Periodic Benefit (Credit) Cost	(3,385)	(1,454)
Other Post-Employment Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	0	0
Interest Cost	3,199	4,580
Expected Return on Plan Assets	0	0
Amortization of Prior Service Credits	(601)	(601)
Amortization of Actuarial Loss	2,319	2,315
Net Periodic Benefit (Credit) Cost	$ 4,917	$ 6,294