Employee and Retiree Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2016

Pension And Other Postretirement Benefits Disclosure [Line Items]

Amounts Included in Accumulated Other Comprehensive Income Not Recognized in Net Periodic Benefit Expense

(Thousands of dollars)	Pension Benefits		Other Postretirement Benefits
Net actuarial loss	$	(247,622)	(2,858)
Prior service (cost) credit		(6,831)	112
	$	(254,453)	(2,746)

Amounts Included in Accumulated Other Comprehensive Income Expected to be Amortized into Net Periodic Benefit Expense

(Thousands of dollars)	Pension Benefits		Other Postretirement Benefits
Net actuarial loss	$	(14,257)	–
Prior service (cost) credit		(1,019)	74
	$	(15,276)	74

Projected Benefit Obligations, Accumulated Benefit Obligations and Fair Value of Plan Assets for Plans where Accumulated Benefit Obligation Exceeded Fair Value of Plan Assets

	Projected Benefit Obligations			Accumulated Benefit Obligations		Fair Value of Plan Assets
(Thousands of dollars)	2016		2015	2016	2015	2016	2015
Funded qualified plans where    accumulated benefit obligation    exceeds fair value of plan assets	$	643,174	630,587	599,730	622,841	497,894	500,695
Unfunded nonqualified and directors'    plans where accumulated benefit    obligation exceeds fair value of    plan assets		156,088	148,019	150,780	140,544	–	–
Unfunded other postretirement plans		106,678	115,222	106,678	115,222	–	–

Components of Net Periodic Benefit Expense

	Pension Benefits				Other Postretirement Benefits
(Thousands of dollars)		2016	2015	2014	2016	2015	2014
Service cost	$	8,136	17,948	22,470	1,864	3,180	2,459
Interest cost		25,185	33,168	33,680	3,800	4,883	4,617
Expected return on plan assets		(28,154)	(34,016)	(33,723)	–	–	–
Amortization of prior service     cost (credit)		1,204	1,560	899	(75)	(82)	(82)
Amortization of transitional    (asset) liability		–	(1)	(480)	–	–	–
Recognized actuarial loss		16,165	15,147	9,471	5	992	5
		22,536	33,806	32,317	5,594	8,973	6,999
Termination benefits expense		–	8,606	–	–	–	–
Curtailment expense		822	306	–	(19)	–	–
Net periodic benefit expense	$	23,358	42,718	32,317	5,575	8,973	6,999

Weighted-Average Assumptions used in Measurement of Benefit Obligations and Net Periodic Benefit Expense

	Benefit Obligations				Net Periodic Benefit Expense
	Pension Benefits		Other Postretirement Benefits		Pension Benefits		Other Postretirement Benefits
	December 31		December 31		Year		Year
	2016	2015	2016	2015	2016	2015	2016	2015
Discount rate	3.94%	4.37%	4.41%	4.61%	3.84%	4.04%	4.24%	4.12%
Expected return on plan assets	5.62%	6.00%	–	–	5.62%	6.00%	–	–
Rate of compensation increase	3.52%	3.74%	–	–	3.52%	3.74%	–	–

Benefit Payments Reflecting Expected Future Service as Appropriate which are Expected to be Paid in Future Years from Assets of Plans or by Company

(Thousands of dollars)	Pension Benefits		Other Postretirement Benefits
2017	$	38,532	6,161
2018		38,896	6,319
2019		39,833	6,435
2020		40,848	6,621
2021		41,653	6,824
2022-2026		221,350	36,326

One Percent Change in Assumed Health Care Cost Trend Rates

(Thousands of dollars)	1% Increase		1% Decrease
Effect on total service and interest cost components of net periodic postretirement     benefit expense for the year ended December 31, 2016	$	1,076	(818)
Effect on the health care component of the accumulated postretirement benefit     obligation at December 31, 2016		15,246	(12,251)

Effects of Fair Value Measurements Using Significant Unobservable Inputs on Changes in Level 3 Plan Assets

(Thousands of dollars)	Hedged Funds and Other Alternative Strategies
Total at December 31, 2014		$	33,952
Actual return on plan assets:
Relating to assets held at the reporting date			(23)
Relating to assets sold during the period			–
Purchases, sales and settlements			–
Total at December 31, 2015			33,929
Actual return on plan assets:
Relating to assets held at the reporting date			185
Relating to assets sold during the period			–
Purchases, sales and settlements			–
Total at December 31, 2016		$	34,114

Domestic Postretirement Plans [Member]

Pension And Other Postretirement Benefits Disclosure [Line Items]

Plans' Benefit Obligations and Fair Value of Assets and Statement of Funded Status

	Pension Benefits			Other Postretirement Benefits
(Thousands of dollars)	2016		2015	2016	2015
Change in benefit obligation
Obligation at January 1	$	794,589	825,552	115,222	118,496
Service cost		8,136	17,948	1,864	3,180
Interest cost		25,185	33,168	3,800	4,883
Plan amendments		–	8,297	–	–
Participant contributions		–	4	1,278	1,276
Actuarial loss (gain)		58,236	(48,019)	(10,627)	(7,436)
Medicare Part D subsidy		–	–	510	510
Exchange rate changes		(30,447)	(15,337)	20	(112)
Benefits paid		(40,928)	(35,936)	(5,369)	(5,575)
Special termination benefits		–	8,606	–	–
Curtailments		822	306	(19)	–
Obligation at December 31		815,593	794,589	106,679	115,222
Change in plan assets
Fair value of plan assets at January 1		521,682	560,978	–	–
Actual return on plan assets		61,860	(18,718)	–	–
Employer contributions		8,186	31,442	3,581	3,789
Participant contributions		–	4	1,278	1,276
Medicare Part D subsidy		–	–	510	510
Exchange rate changes		(30,609)	(14,104)	–	–
Benefits paid		(40,928)	(35,936)	(5,369)	(5,575)
Other		(834)	(1,984)	–	–
Fair value of plan assets at December 31		519,357	521,682	–	–
Funded status and amounts recognized in the     Consolidated Balance Sheets at December 31
Deferred charges and other assets		7,591	7,463	–	–
Other accrued liabilities		(8,184)	(7,487)	(5,267)	(5,370)
Deferred credits and other liabilities		(295,643)	(272,883)	(101,412)	(109,852)
Funded status and net plan liability recognized             at December 31	$	(296,236)	(272,907)	(106,679)	(115,222)

Foreign Other Postretirement Benefit Plans [Member]

Pension And Other Postretirement Benefits Disclosure [Line Items]

Plans' Benefit Obligations and Fair Value of Assets and Statement of Funded Status

	Pension Benefits			Other Postretirement Benefits
(Thousands of dollars)	2016		2015	2016	2015
Benefit obligation at December 31	$	206,502	197,549	615	643
Fair value of plan assets at December 31		197,575	193,933	–	–
Net plan liabilities recognized		8,927	3,616	615	643
Net periodic benefit expense (benefit)		(2,244)	4,703	154	152

Other Postretirement Benefits [Member]

Pension And Other Postretirement Benefits Disclosure [Line Items]

Asset Allocation for Benefit Plans

At December 31, 2016, the fair value measurements of retirement plan assets within the fair value hierarchy are included in the table that follows.

			Fair Value Measurements Using
(Thousands of dollars)	Fair Value at December 31, 2016		Quoted Prices in Active Markets for Identical Assets (Level 1)	Significant Other Observable Inputs (Level 2)	Significant Unobservable Inputs (Level 3)
Domestic Plans
Equity securities:
U.S. core equity	$	61,554	61,554	–	–
U.S. small/midcap		23,103	23,103	–	–
Hedged funds and other          alternative strategies		48,113	–	13,999	34,114
International commingled          trust fund		67,451	–	67,451	–
Emerging market commingled         equity fund		16,006	–	16,006	–
Fixed income securities:
U.S. fixed income		78,473	–	78,473	–
International commingled          trust fund		13,486	–	13,486	–
Emerging market mutual fund		5,775	–	5,775	–
Cash and equivalents		7,821	7,821	–	–
Total Domestic Plans		321,782	92,478	195,190	34,114
Foreign Plans
Equity securities funds		74,108	–	74,108	–
Fixed income securities funds		97,075	–	97,075	–
Diversified pooled fund		21,463	–	21,463	–
Cash and equivalents		4,929	–	4,929	–
Total Foreign Plans		197,575	–	197,575	–
Total	$	519,357	92,478	392,765	34,114

At December 31, 2015, the fair value measurements of retirement plan assets within the fair value hierarchy are included in the table that follows.

			Fair Value Measurements Using
(Thousands of dollars)	Fair Value at December 31, 2015		Quoted Prices in Active Markets for Identical Assets (Level 1)	Significant Other Observable Inputs (Level 2)	Significant Unobservable Inputs (Level 3)
Domestic Plans
Equity securities:
U.S. core equity	$	51,878	51,878	–	–
U.S. small/midcap		26,964	26,964	–	–
Hedged funds and other          alternative strategies		50,878	–	16,949	33,929
International commingled          trust fund		72,205	–	72,205	–
Emerging market commingled         equity fund		16,873	–	16,873	–
Fixed income securities:
U.S. fixed income		80,681	–	80,681	–
International commingled          trust fund		15,332	–	15,332	–
Emerging market mutual fund		6,439	–	6,439	–
Cash and equivalents		6,499	6,499	–	–
Total Domestic Plans		327,749	85,341	208,479	33,929
Foreign Plans
Equity securities funds		104,718	–	104,718	–
Fixed income securities funds		67,494	–	67,494	–
Diversified pooled fund		20,987	–	20,987	–
Cash and equivalents		734	734	–	–
Total Foreign Plans		193,933	734	193,199	–
Total	$	521,682	86,075	401,678	33,929

Funded Defined Benefit Pension Plans [Member]

Pension And Other Postretirement Benefits Disclosure [Line Items]

Asset Allocation for Benefit Plans

	December 31,
	2016		2015
Equity securities	58.4	%	64.4	%
Fixed income securities	39.0		34.0
Cash equivalents	2.6		1.6
	100.0	%	100.0	%