EMPLOYEE BENEFIT PLANS (Tables)

6 Months Ended

Jun. 30, 2020

Employee Benefit Plans [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

The following tables set forth the components of net periodic benefit cost for our pension and other postemployment benefit plans for the periods indicated:

	Pension Benefits
	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2020			2019			2020			2019
	(Thousands of dollars)
Components of net periodic benefit cost
Service cost	$	3,217		$	3,008		$	6,434		$	6,016
Interest cost	8,545			10,168			17,090			20,336
Expected return on assets	(15,280		)	(15,485		)	(30,560		)	(30,970		)
Amortization of net loss	10,580			8,260			21,160			16,520
Net periodic benefit cost	$	7,062		$	5,951		$	14,124		$	11,902

	Other Postemployment Benefits
	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2020			2019			2020			2019
	(Thousands of dollars)
Components of net periodic benefit cost (credit)
Service cost	$	423		$	434		$	846		$	868
Interest cost	1,889			2,329			3,778			4,658
Expected return on assets	(3,867		)	(3,147		)	(7,734		)	(6,294		)
Amortization of unrecognized prior service credit	(29		)	(168		)	(58		)	(336		)
Amortization of net loss	43			561			86			1,122
Net periodic benefit cost (credit)	$	(1,541	)	$	9		$	(3,082	)	$	18