EMPLOYEE BENEFIT PLANS - Funded Status of Pension Plan (Details) - Pension Plans - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amounts recognized in the Consolidated Balance Sheets
Noncurrent asset	$ 63,857	$ 72,320
Current liability	(3,776)	(3,863)
Noncurrent liability	(265,178)	(413,829)
Net amount recognized	(205,097)	(345,372)
Amounts recognized in accumulated other comprehensive loss (pre-tax)
Prior service cost	3,816	13,798
Net actuarial loss	855,300	869,907
Net amount recognized	$ 859,116	$ 883,705