PENSION AND OTHER POSTRETIREMENT BENEFITS - Schedule of Defined Benefit Plans Disclosure (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 1,688	$ 1,719
Interest Cost	3,763	4,229
Expected Return on Plan Assets	(5,452)	(5,193)
Amortizations:
Prior Service Cost	26	26
Actuarial Loss	2,715	2,437
Net Periodic Benefit Cost	2,740	3,218
Capitalized Benefit Cost	(544)	(594)
Deferred Benefit Cost	(408)	(541)
Total Net Periodic Benefit Expense	1,788	2,083
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service Cost	165	234
Interest Cost	608	628
Expected Return on Plan Assets	(1,346)	(1,149)
Amortizations:
Prior Service Cost	(144)	(143)
Actuarial Loss	192	263
Net Periodic Benefit Cost	(525)	(167)
Capitalized Benefit Cost	(108)	(56)
Deferred Benefit Cost	396	116
Total Net Periodic Benefit Expense	$ (237)	$ (107)