CLOSURE AND POST-CLOSURE LIABILITIES - Anticipated Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Environmental Property Sale, Disposal or Abandonment Costs
2022	$ 12,612
2023	11,452
2024	13,460
2025	10,791
2026	8,143
Thereafter	276,236
Undiscounted closure and post-closure liabilities	332,694
Less: Discount at credit-adjusted risk-free rate	(158,941)
Less: Undiscounted estimated closure and post-closure liabilities relating to airspace not yet consumed	(74,650)
Present value of closure and post-closure liabilities	$ 99,103	$ 87,926	$ 75,651