EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Tables)

12 Months Ended

Dec. 31, 2017

Pension and postretirement benefit plans obligations and fair value of plan assets

Obligations and Funded Status - The following tables set forth our pension and postretirement benefit plans benefit obligations and fair value of plan assets for the periods indicated:



	Pension Benefits						Postretirement Benefits
	December 31,						December 31,
	2017			2016			2017			2016
Change in benefit obligation	(Thousands of dollars)
Benefit obligation, beginning of period	$	428,386		$	390,688		$	54,823		$	49,496
Service cost	6,896			6,501			662			596
Interest cost	18,645			19,820			2,261			2,404
Plan participants’ contributions	—			—			901			894
Actuarial loss	41,678			24,458			3,456			4,905
Benefits paid	(13,990		)	(13,081		)	(4,165		)	(3,472		)
Benefit obligation, end of period	481,615			428,386			57,938			54,823

Change in plan assets
Fair value of plan assets, beginning of period	261,671			258,635			29,550			28,641
Actual return on plan assets	50,827			16,117			5,385			1,902
Employer contributions	7,500			—			2,000			1,000
Plan participants’ contributions	—			—			901			894
Benefits paid	(13,990		)	(13,081		)	(3,703		)	(2,887		)
Fair value of plan assets, end of period	306,008			261,671			34,133			29,550
Balance at December 31	$	(175,607	)	$	(166,715	)	$	(23,805	)	$	(25,273	)

Current liabilities	$	(4,544	)	$	(4,363	)	$	—		$	—
Noncurrent liabilities	(171,063		)	(162,352		)	(23,805		)	(25,273		)
Balance at December 31	$	(175,607	)	$	(166,715	)	$	(23,805	)	$	(25,273	)

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

Components of Net Periodic Benefit Cost - The following table sets forth the components of net periodic benefit cost for our pension and postretirement benefit plans for the periods indicated:



	Pension Benefits									Postretirement Benefits
	Years Ended December 31,									Years Ended December 31,
	2017			2016			2015			2017			2016			2015
	(Thousands of dollars)
Components of net periodic benefit cost
Service cost	$	6,896		$	6,501		$	7,565		$	662		$	596		$	743
Interest cost	18,645			19,820			18,218			2,261			2,404			2,347
Expected return on plan assets	(21,376		)	(20,348		)	(20,900		)	(2,257		)	(2,124		)	(2,253		)
Amortization of prior service cost (credit)	—			—			94			(1,662		)	(1,662		)	(1,662		)
Amortization of net loss	13,586			10,966			15,981			1,679			1,046			1,743
Net periodic benefit cost	$	17,751		$	16,939		$	20,958		$	683		$	260		$	918

Amounts recognized in other comprehensive income (loss)

Other Comprehensive Income (Loss) - The following table sets forth the amounts recognized in other comprehensive income (loss) related to our pension benefits and postretirement benefits for the periods indicated:



	Pension Benefits									Postretirement Benefits
	Years Ended December 31,									Years Ended December 31,
	2017			2016			2015			2017			2016			2015
	(Thousands of dollars)
Net gain (loss) arising during the period	$	(16,572	)	$	(33,043	)	$	5,145		$	(328	)	$	(5,128	)	$	4,393
Amortization of prior service cost (credit)	—			—			94			(1,662		)	(1,662		)	(1,662		)
Amortization of net loss	13,586			10,966			15,981			1,679			1,046			1,743
Deferred income taxes	(960		)	8,831			(8,488		)	82			2,297			(1,790		)
Total recognized in other comprehensive income (loss)	$	(3,946	)	$	(13,246	)	$	12,732		$	(229	)	$	(3,447	)	$	2,684

Amounts in accumulated other comprehensive income (loss)

The table below sets forth the amounts in accumulated other comprehensive loss that had not yet been recognized as components of net periodic benefit expense for the periods indicated:



	Pension Benefits						Postretirement Benefits
	December 31,						December 31,
	2017			2016			2017			2016
	(Thousands of dollars)
Prior service credit (cost)	$	—		$	—		$	1,889		$	3,550
Accumulated loss	(160,921		)	(157,935		)	(12,991		)	(14,341		)
Accumulated other comprehensive loss	(160,921		)	(157,935		)	(11,102		)	(10,791		)
Deferred income taxes	62,214			63,174			4,398			4,316
Accumulated other comprehensive loss, net of tax	$	(98,707	)	$	(94,761	)	$	(6,704	)	$	(6,475	)

Amounts in accumulated comprehensive income (loss) expected to be recognized as components of net periodic benefit expense

The following table sets forth the amounts recognized in accumulated comprehensive loss expected to be recognized as components of net periodic benefit expense in the next fiscal year.



	Pension Benefits		Postretirement Benefits
Amounts to be recognized in 2018	(Thousands of dollars)
Prior service (credit) cost	$	—	$	(1,662	)
Net loss	$	17,060	$	1,338

Weighted-average assumptions used to determine benefit obligations and net periodic benefit costs

Actuarial Assumptions - The following table sets forth the weighted-average assumptions used to determine benefit obligations for pension and postretirement benefits for the periods indicated:



	Pension Benefits		Postretirement Benefits
	December 31,		December 31,
	2017	2016	2017	2016
Discount rate (a)	3.75%	4.50%	3.75%	4.25%
Compensation increase rate	3.00%	3.10%	N/A	N/A

(a) The decrease in the discount rate at December 31, 2017, compared with 2016, resulted primarily from narrower credit spreads associated with the bonds in the hypothetical portfolio discussed below.

The following table sets forth the weighted-average assumptions used to determine net periodic benefit costs for the periods indicated:



	Years Ended December 31,
	2017	2016	2015
Discount rate - pension plans	4.50%	5.25%	4.50%
Discount rate - postretirement plans	4.25%	5.00%	4.25%
Expected long-term return on plan assets	7.75%	7.75%	8.00%
Compensation increase rate	3.10%	3.10%	3.15%

Assumed health care cost trend rates

Health Care Cost Trend Rates - The following table sets forth the assumed health care cost-trend rates for the periods indicated:



	2017	2016
Health care cost-trend rate assumed for next year	7.00%	7.25%
Rate to which the cost-trend rate is assumed to decline (the ultimate trend rate)	5.00%	5.00%
Year that the rate reaches the ultimate trend rate	2022	2022

Schedule of allocation of plan assets

Plan Assets - Our investment strategy is to invest plan assets in accordance with sound investment practices that emphasize long-term fundamentals. The goal of this strategy is to maximize investment returns while managing risk in order to meet the plan’s current and projected financial obligations. The investment policy follows a glide path approach toward liability-driven investing that shifts a higher portfolio weighting to fixed income as the plan's funded status increases. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The plan’s current investments include a diverse blend of various domestic and international equities, investments in various classes of debt securities, insurance contracts and venture capital. The target allocation for the assets of our pension plan as of December 31, 2017, is as follows:



U.S. large-cap equities	37	%
Long duration bonds	30	%
Developed foreign large-cap equities	10	%
Alternative investments	8	%
Mid-cap equities	6	%
Emerging markets equities	5	%
Small-cap equities	4	%
Total	100	%

As part of our risk management for the plans, minimums and maximums have been set for each of the asset classes listed above. All investment managers for the plan are subject to certain restrictions on the securities they purchase and, with the exception of indexing purposes, are prohibited from owning our stock.

The following tables set forth our pension benefits and postretirement benefits plan assets by fair value category as of the measurement date:



	Pension Benefits
	December 31, 2017
Asset Category	Level 1		Level 2		Level 3		Subtotal		Measured at NAV (d)		Total
	(Thousands of dollars)
Investments:
Equity securities (a)	$	176,347	$	19,199	$	—	$	195,546	$	—	$	195,546
Government obligations	—		19,481		—		19,481		—		19,481
Corporate obligations (b)	—		62,981		—		62,981		—		62,981
Common/collective trusts	—		6,621		—		6,621		—		6,621
Cash	298		—		—		298		—		298
Other investments (c)	—		—		—		—		21,081		21,081
Fair value of plan assets	$	176,645	$	108,282	$	—	$	284,927	$	21,081	$	306,008

(a) - This category represents securities of the respective market sector from diverse industries.

(b) - This category represents bonds from diverse industries.

(c) - This category represents alternative investments in limited partnerships, which can be redeemed with a 30-day notice with no further restrictions. There are no unfunded capital commitments.

(d) - Plan asset investments measured at fair value using the net asset value per share.



	Pension Benefits
	December 31, 2016
Asset Category	Level 1		Level 2		Level 3		Subtotal		Measured at NAV (d)		Total
	(Thousands of dollars)
Investments:
Equity securities (a)	$	146,980	$	13,606	$	—	$	160,586	$	—	$	160,586
Government obligations	—		17,979		—		17,979		—		17,979
Corporate obligations (b)	—		56,484		—		56,484		—		56,484
Common/collective trusts	—		6,577		—		6,577		—		6,577
Cash	43		—		—		43		—		43
Other investments (c)	—		—		—		—		20,002		20,002
Fair value of plan assets	$	147,023	$	94,646	$	—	$	241,669	$	20,002	$	261,671

(a) - This category represents securities of the respective market sector from diverse industries.

(b) - This category represents bonds from diverse industries.

(c) - This category represents alternative investments in limited partnerships, which can be redeemed with a 30-day notice with no further restrictions. There are no unfunded capital commitments.

(d) - Plan asset investments measured at fair value using the net asset value per share.



	Postretirement Benefits
	December 31, 2017
Asset Category	Level 1		Level 2		Level 3		Total
	(Thousands of dollars)
Investments:
Equity securities (a)	$	1,951	$	—	$	—	$	1,951
Money market funds	—		1,515		—		1,515
Insurance and group annuity contracts	—		30,667		—		30,667
Fair value of plan assets	$	1,951	$	32,182	$	—	$	34,133

(a) - This category represents securities of the respective market sector from diverse industries.



	Postretirement Benefits
	December 31, 2016
Asset Category	Level 1		Level 2		Level 3		Total
	(Thousands of dollars)
Investments:
Equity securities (a)	$	1,777	$	—	$	—	$	1,777
Money market funds	—		1,259		—		1,259
Insurance and group annuity contracts	—		26,514		—		26,514
Fair value of plan assets	$	1,777	$	27,773	$	—	$	29,550

(a) - This category represents securities of the respective market sector from diverse industries.

Pension benefits and postretirement benefit payments expected to be paid

The following table sets forth the pension benefits and postretirement benefits payments expected to be paid in 2018 through 2027:



	Pension Benefits		Postretirement Benefits
Benefits to be paid in:	(Thousands of dollars)
2018	$	16,796	$	3,452
2019	$	18,011	$	3,653
2020	$	18,970	$	3,859
2021	$	20,206	$	3,993
2022	$	21,157	$	4,023
2023 through 2027	$	117,048	$	19,302