Pension plans and other postretirement benefits (Tables)

12 Months Ended

Dec. 31, 2017

Compensation And Retirement Disclosure [Abstract]

Net Periodic Pension Expense for Defined Benefit Plans

Net periodic pension expense for defined benefit plans consisted of the following:

	Year Ended December 31
	2017			2016			2015
	(In thousands)
Service cost	$	20,193		$	25,037		$	24,372
Interest cost on benefit obligation		79,270			83,410			72,731
Expected return on plan assets		(108,524	)		(108,473	)		(96,155	)
Amortization of prior service cost (credit)		557			(3,228	)		(6,005	)
Recognized net actuarial loss		29,263			30,145			44,825
Net periodic pension expense	$	20,759		$	26,891		$	39,768

Net other postretirement benefits expense for defined benefit plans consisted of the following:

	Year Ended December 31
	2017			2016			2015
	(In thousands)
Service cost	$	1,172		$	1,595		$	914
Interest cost on benefit obligation		3,716			4,971			2,995
Amortization of prior service credit		(1,359	)		(1,359	)		(1,359	)
Recognized net actuarial (gain) loss		(988	)		60			106
Net other postretirement benefits expense	$	2,541		$	5,267		$	2,656

Data Relating to Funding Position of Defined Benefit Plans

Data relating to the funding position of the defined benefit plans were as follows:

	Pension Benefits						Other Postretirement Benefits
	2017			2016			2017			2016
	(In thousands)
Change in benefit obligation:
Benefit obligation at beginning of year	$	2,007,158		$	2,004,531		$	109,922		$	121,497
Service cost		20,193			25,037			1,172			1,595
Interest cost		79,270			83,410			3,716			4,971
Plan participants’ contributions		—			—			2,929			3,085
Amendments and curtailments		—			(28,308	)		(30,088	)		—
Actuarial (gain) loss		172,180			4,827			(8,511	)		(10,553	)
Medicare Part D reimbursement		—			—			630			592
Benefits paid		(90,065	)		(82,339	)		(11,133	)		(11,265	)
Benefit obligation at end of year		2,188,736			2,007,158			68,637			109,922
Change in plan assets:
Fair value of plan assets at beginning of year		1,642,131			1,625,134			—			—
Actual return on plan assets		251,381			88,564			—			—
Employer contributions		211,444			10,772			7,574			7,588
Plan participants’ contributions		—			—			2,929			3,085
Medicare Part D reimbursement		—			—			630			592
Benefits paid		(90,065	)		(82,339	)		(11,133	)		(11,265	)
Fair value of plan assets at end of year		2,014,891			1,642,131			—			—
Funded status	$	(173,845	)	$	(365,027	)	$	(68,637	)	$	(109,922	)
Accrued liabilities recognized in the consolidated    balance sheet	$	(173,845	)	$	(365,027	)	$	(68,637	)	$	(109,922	)
Amounts recognized in accumulated other    comprehensive income (“AOCI”) were:
Net loss (gain)	$	460,622		$	460,562		$	(13,936	)	$	(6,413	)
Net prior service cost (credit)		2,948			3,505			(36,466	)		(7,737	)
Pre-tax adjustment to AOCI		463,570			464,067			(50,402	)		(14,150	)
Taxes		(121,873	)		(182,611	)		13,251			5,568
Net adjustment to AOCI	$	341,697		$	281,456		$	(37,151	)	$	(8,582	)

Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income

The table below reflects the changes in plan assets and benefit obligations recognized in other comprehensive income related to the Company’s postretirement benefit plans.

	Pension Plans			Other Postretirement Benefit Plans			Total
	(In thousands)
2017
Net loss (gain)	$	29,323		$	(8,511	)	$	20,812
Amendments and curtailments		—			(30,088	)		(30,088	)
Amortization of prior service (cost) credit		(557	)		1,359			802
Amortization of actuarial (loss) gain		(29,263	)		988			(28,275	)
Total recognized in other comprehensive income,    pre-tax	$	(497	)	$	(36,252	)	$	(36,749	)
2016
Net loss (gain)	$	24,736		$	(10,553	)	$	14,183
Amendments and curtailments		(28,308	)		—			(28,308	)
Amortization of prior service credit		3,228			1,359			4,587
Amortization of actuarial loss		(30,145	)		(60	)		(30,205	)
Total recognized in other comprehensive income,    pre-tax	$	(30,489	)	$	(9,254	)	$	(39,743	)

Amortization of Amounts in Accumulated Other Comprehensive Income Expected to be Recognized as Components of Net Periodic Benefit Expense

The following table reflects the amortization of amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit expense during 2018:

	Pension Plans		Other Postretirement Benefit Plans
	(In thousands)
Amortization of net prior service cost (credit)	$	557	$	(4,729	)
Amortization of net loss (gain)		44,416		(830	)

Assumed Weighted-Average Rates Used to Determine Benefit Obligations

The assumed weighted-average rates used to determine benefit obligations at December 31 were:

	Pension Benefits						Other Postretirement Benefits
	2017			2016			2017			2016
Discount rate		3.50	%		4.00	%		3.50	%		4.00	%
Rate of increase in future compensation levels		4.33	%		4.39	%		—			—

Assumed Weighted-Average Rates Used to Determine Net Benefit Expense

The assumed weighted-average rates used to determine net benefit expense for the years ended December 31 were:

	Pension Benefits									Other Postretirement Benefits
	2017			2016			2015			2017			2016			2015
Discount rate		4.00	%		4.25	%		4.00	%		4.00	%		4.25	%		4.00	%
Long-term rate of return on plan assets		6.50	%		6.50	%		6.50	%		—			—			—
Rate of increase in future compensation    levels		4.39	%		4.37	%		4.39	%		—			—			—

Effects on One-Percentage Point Change in Assumed Health Care Cost Trend Rates

A one-percentage point change in assumed health care cost trend rates would have had the following effects:

	+1%			-1%
	(In thousands)
Increase (decrease) in:
Service and interest cost	$	63	$	(57	)
Accumulated postretirement benefit obligation		1,454		(1,316	)

Fair Values of Company's Pension Plan Assets by Asset Category

The fair values of the Company’s pension plan assets at December 31, 2017 and 2016, by asset category, were as follows:

	Fair Value Measurement of Plan Assets At December 31, 2017
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(In thousands)
Asset category:
Money-market investments	$	117,648	$	62,706	$	54,942	$	—
Equity securities:
M&T		154,818		154,818		—		—
Domestic(a)		240,763		240,763		—		—
International(b)		13,349		13,349		—		—
Mutual funds:
Domestic(a)		205,509		205,509		—		—
International(b)		405,200		405,200		—		—
		1,019,639		1,019,639		—		—
Debt securities:
Corporate(c)		89,751		—		89,751		—
Government		235,984		—		235,984		—
International		2,176		—		2,176		—
Mutual funds:
Domestic(d)		243,456		243,456		—		—
		571,367		243,456		327,911		—
Other:
Diversified mutual fund		80,227		80,227		—		—
Real estate partnerships		3,747		842		—		2,905
Private equity		31,484		—		—		31,484
Hedge funds		178,080		125,966		—		52,114
Guaranteed deposit fund		10,925		—		—		10,925
		304,463		207,035		—		97,428
Total(e)	$	2,013,117	$	1,532,836	$	382,853	$	97,428

	Fair Value Measurement of Plan Assets At December 31, 2016
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(In thousands)
Asset category:
Money-market investments	$	39,556	$	35,562	$	3,994	$	—
Equity securities:
M&T		164,474		164,474		—		—
Domestic(a)		200,595		200,595		—		—
International(b)		14,364		14,364		—		—
Mutual funds:
Domestic(a)		250,472		250,472		—		—
International(b)		290,172		290,172		—		—
		920,077		920,077		—		—
Debt securities:
Corporate(c)		104,909		—		104,909		—
Government		121,869		—		121,869		—
International		13,073		—		13,073		—
Mutual funds:
Domestic(d)		205,847		205,847		—		—
		445,698		205,847		239,851		—
Other:
Diversified mutual fund		92,691		92,691		—		—
Real estate partnerships		3,112		768		—		2,344
Private equity		21,924		—		—		21,924
Hedge funds		106,250		85,270		—		20,980
Guaranteed deposit fund		10,992		—		—		10,992
		234,969		178,729		—		56,240
Total(e)	$	1,640,300	$	1,340,215	$	243,845	$	56,240

(a) This category is mainly comprised of equities of companies primarily within the mid-cap and large-cap sectors of the U.S. economy and range across diverse industries.

(b) This category is comprised of equities in companies primarily within the mid-cap and large-cap sectors of international markets mainly in developed markets in Europe and the Pacific Rim.

(c) This category represents investment grade bonds of U.S. issuers from diverse industries.

(d) Approximately 77% of the mutual funds were invested in investment grade bonds and 23% in high-yielding bonds at December 31, 2017. Approximately 75% of the mutual funds were invested in investment grade bonds and 25% in high-yielding bonds at December 31, 2016. The holdings within the funds were spread across diverse industries.

(e) Excludes dividends and interest receivable totaling $1,774,000 and $1,831,000 at December 31, 2017 and 2016, respectively.

Changes in Level 3 Pension Plan Assets Measured at Fair Value on Recurring Basis

The changes in Level 3 pension plan assets measured at estimated fair value on a recurring basis during the year ended December 31, 2017 were as follows:

	Balance – January 1, 2017		Purchases (Sales)		Total Realized/ Unrealized Gains (Losses)			Balance – December 31, 2017
	(In thousands)
Other
Real estate partnerships	$	2,344	$	365	$	196		$	2,905
Private equity		21,924		6,821		2,739			31,484
Hedge funds		20,980		29,839		1,295			52,114
Guaranteed deposit fund		10,992		—		(67	)		10,925
Total	$	56,240	$	37,025	$	4,163		$	97,428

Defined Benefit Plan Estimated Future Benefit Payments

Estimated benefits expected to be paid in future years related to the Company’s defined benefit pension and other postretirement benefits plans are as follows:

	Pension Benefits		Other Postretirement Benefits
	(In thousands)
Year ending December 31:
2018	$	88,407	$	7,318
2019		94,317		7,207
2020		98,753		7,055
2021		103,968		4,402
2022		107,298		4,302
2023 through 2027		594,900		19,830