EMPLOYEE BENEFIT PLANS (Tables)

9 Months Ended

Sep. 30, 2018

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						Nine Months Ended
	September 30,						September 30,
	2018			2017			2018			2017
	(Thousands of dollars)
Components of net periodic benefit cost
Service cost	$	3,230		$	3,044		$	9,690		$	9,132
Interest cost (a)	9,200			10,113			27,600			30,339
Expected return on assets (a)	(15,145		)	(14,624		)	(45,435		)	(43,872		)
Amortization of net loss (a)	9,978			9,027			29,934			27,081
Net periodic benefit cost	$	7,263		$	7,560		$	21,789		$	22,680

(a) Since adoption of ASU 2017-07 on January 1, 2018, these amounts, net of any amounts capitalized as a regulatory asset, have been recognized as other income (expense) in the Consolidated Statements of Income. See Note 11 for additional detail of our other income (expense).

	Other Postemployment Benefits
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2018			2017			2018			2017
	(Thousands of dollars)
Components of net periodic benefit (credit) cost
Service cost	$	589		$	627		$	1,767		$	1,881
Interest cost (a)	2,279			2,472			6,837			7,416
Expected return on assets (a)	(3,571		)	(3,147		)	(10,713		)	(9,441		)
Amortization of unrecognized prior service cost (a)	(1,142		)	(1,149		)	(3,426		)	(3,447		)
Amortization of net loss (a)	972			1,621			2,916			4,863
Net periodic benefit (credit) cost	$	(873	)	$	424		$	(2,619	)	$	1,272

(a) Since adoption of ASU 2017-07 on January 1, 2018, these amounts, net of any amounts capitalized as a regulatory asset, have been recognized as other income (expense) in the Consolidated Statements of Income. See Note 11 for additional detail of our other income (expense).