v3.20.4
UNIT-BASED COMPENSATION Narrative 4 (Details) - USD ($)
12 Months Ended
Feb. 01, 2021
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Performance Units [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total fair value of restricted units that vested during the period   $ 4,200,000 $ 2,100,000  
Units issued to satisfy award vestings, net of tax (units)   93,440 50,054  
Unit-based awards, vested (units)   (147,390) (80,690) 0
Performance cash awards        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Performance cash awards granted, amount   $ 2,200,000    
Performance cash awards | Subsequent Event [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Units issued in connection with performance cash awards 58,070