Benefit Plans and Other Postretirement Benefits (Tables)

9 Months Ended

Sep. 30, 2016

Compensation and Retirement Disclosure [Abstract]

Components of Net Periodic Benefit Cost

Components of Net Periodic Benefit Cost

	Three Months Ended Sept. 30
	2016			2015			2016			2015
(Thousands of Dollars)	Pension Benefits						Postretirement Health Care Benefits
Service cost	$	1,104		$	1,190		$	6		$	7
Interest cost	1,704			1,630			163			164
Expected return on plan assets	(2,289		)	(2,371		)	(6		)	(8		)
Amortization of prior service cost (credit)	28			27			(88		)	(87		)
Amortization of net loss	1,348			1,701			83			114
Net benefit cost recognized for financial reporting	$	1,895		$	2,177		$	158		$	190

	Nine Months Ended Sept. 30
	2016			2015			2016			2015
(Thousands of Dollars)	Pension Benefits						Postretirement Health Care Benefits
Service cost	$	3,312		$	3,570		$	18		$	21
Interest cost	5,112			4,890			489			490
Expected return on plan assets	(6,867		)	(7,113		)	(18		)	(23		)
Amortization of prior service cost (credit)	84			83			(264		)	(263		)
Amortization of net loss	4,044			5,103			249			342
Net benefit cost recognized for financial reporting	$	5,685		$	6,533		$	474		$	567