CLOSURE AND POST-CLOSURE LIABILITIES (Anticipated Payments) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Environmental Property Sale, Disposal or Abandonment Costs
2017	$ 6,931
2018	8,181
2019	9,916
2020	8,646
2021	5,093
Thereafter	288,167
Undiscounted closure and post-closure liabilities	326,934
Less: Discount at credit-adjusted risk-free rate	(164,350)
Less: Undiscounted estimated closure and post-closure liabilities relating to airspace not yet consumed	(104,253)
Present value of closure and post-closure liabilities	$ 58,331	$ 56,249	$ 50,701