v3.20.4
ACCRUED LIABILITIES (Tables)
12 Months Ended
Dec. 31, 2020
Accrued Liabilities, Current [Abstract]  
Schedule of Accrued Liabilities [Table Text Block]
Accrued liabilities consisted of the following:
 December 31,
 20202019
 (Thousands of Dollars)
Employee wages and benefit costs$27,805 $36,704 
Revenue contract liabilities22,019 21,083 
Interest rate swaps— 19,169 
Operating lease liabilities10,890 10,416 
Environmental costs5,371 4,837 
Other11,685 16,401 
Accrued liabilities$77,770 $108,610