EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Tables)

9 Months Ended

Sep. 30, 2019

Defined Benefit Plan [Abstract]

Components of net periodic benefit cost for retirement and postretirement benefit plans

The following tables set forth the components of net periodic benefit cost (income) for our retirement and other postretirement benefit plans for the periods indicated:

	Retirement Benefits
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2019			2018			2019			2018
	(Thousands of dollars)
Components of net periodic benefit cost
Service cost	$	1,954		$	1,832		$	5,862		$	5,496
Interest cost	5,126			4,408			15,378			13,224
Expected return on plan assets	(5,892		)	(5,969		)	(17,676		)	(17,907		)
Amortization of net loss	3,158			4,258			9,474			12,774
Net periodic benefit cost	$	4,346		$	4,529		$	13,038		$	13,587

	Other Postretirement Benefits
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2019			2018			2019			2018
	(Thousands of dollars)
Components of net periodic benefit cost
Service cost	$	117		$	211		$	351		$	633
Interest cost	509			527			1,527			1,581
Expected return on plan assets	(570		)	(672		)	(1,710		)	(2,016		)
Amortization of prior service credit	(57		)	(415		)	(171		)	(1,245		)
Amortization of net loss	74			334			222			1,002
Net periodic benefit cost (income)	$	73		$	(15	)	$	219		$	(45	)