EMPLOYEE BENEFIT PLANS (Tables)

6 Months Ended

Jun. 30, 2017

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,
	2017			2016			2017			2016
	(Thousands of dollars)
Components of net periodic benefit cost
Service cost	$	3,044		$	3,014		$	6,088		$	6,028
Interest cost	10,113			11,388			20,226			22,775
Expected return on assets	(14,624		)	(15,296		)	(29,248		)	(30,592		)
Amortization of net loss	9,027			8,885			18,054			17,771
Net periodic benefit cost	$	7,560		$	7,991		$	15,120		$	15,982

	Other Postemployment Benefits
	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2017			2016			2017			2016
	(Thousands of dollars)
Components of net periodic benefit cost
Service cost	$	627		$	638		$	1,254		$	1,276
Interest cost	2,472			2,627			4,944			5,254
Expected return on assets	(3,147		)	(3,071		)	(6,294		)	(6,142		)
Amortization of unrecognized prior service cost	(1,149		)	(908		)	(2,298		)	(1,816		)
Amortization of net loss	1,621			1,151			3,242			2,302
Net periodic benefit cost	$	424		$	437		$	848		$	874