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UNIT INCENTIVE PLAN (Narrative) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Equity compensation expense $ 1,185 $ 1,127 $ 1,128
Accrued liabilities relating to incentive compensation program $ 2,500 1,900  
Performance based, RSU's      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Compensation expense vesting period 4 years    
Portion of accrued liabilities paid in cash $ 662 $ 597  
Restricted Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Compensation expense vesting period 4 years    
Restricted Units | Directors      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted to directors in payment of board compensation (in shares) 1,574 1,637 2,213
LTIP      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Performance period 3 years    
Portion of accrued liabilities paid in cash $ 1,800 $ 1,300  
2005 Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Authorized for issuance (in shares) 1,105,815    
Authorized but unissued (in shares) 841,861    
Unvested Restricted Stock Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total compensation expense related to non-vested awards not yet recognized $ 1,600    
Weighted average remaining period to vest 36 months