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EMPLOYEE BENEFIT PLANS - Multi-employer (Details) - Pension Plan - USD ($)
$ in Thousands
12 Months Ended
Jun. 12, 2012
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Jan. 01, 2019
Pension Plans          
Pension expense   $ 2,722 $ 3,114 $ 2,988  
Consenting agreement entered with local bargaining union          
Pension Plans          
Percentage of funded status         50.40%
Employer contributions to multi-employer defined benefit pension plans   $ 2,850 2,943 2,836  
Insolvent period   20 years      
Estimated liability upon withdrawal from plan   $ 99,300 99,800 81,600  
Percentage of annual compounded surcharge for rehabilitation   5.00%      
Percentage of interim surcharge 5.00%        
Pension expense   $ 2,866 2,961 2,836  
Surcharges   $ 1,010 $ 948 $ 811