v3.21.1
DEBT (Tables)
3 Months Ended
Mar. 31, 2021
Debt Disclosure [Abstract]  
Fair Value and Carrying Value of Debt [Table Text Block]
The estimated fair values and carrying amounts of long-term debt, excluding finance leases, were as follows:
March 31, 2021December 31, 2020
 (Thousands of Dollars)
Fair value$3,666,778 $3,799,378 
Carrying amount$3,392,617 $3,539,258