Pension Plan and Postretirement Benefits Other Than Pension (Tables)

12 Months Ended

Dec. 31, 2015

Pension Plan and Postretirement Benefits Other Than Pension

Schedule of changes in net funded status, disclosure of amounts recognized in the balance sheet, and the assumptions used to determine the benefit obligation

	Pension Benefits						Other Postretirement Benefits
	2015		2014		2013		2015		2014		2013
	(in thousands)
Change in projected benefit obligation:
Net benefit obligation at beginning of year	$	208,085		172,105		184,165		9,902		8,172		8,792
Service cost		12,080		10,084		11,011		910		719		788
Interest cost		8,420		8,395		7,711		397		397		361
Benefits paid		(10,184)		(8,733)		(19,283)		(505)		(527)		(283)
Actuarial (gain) loss		(7,618)		26,410		(11,499)		(2,632)		760		(1,807)
Plan amendments		—		(176)		—		—		—		—
Retiree contributions		—		—		—		349		381		321
Net benefit obligation at end of year	$	210,783		208,085		172,105		8,421		9,902		8,172

Schedule of pension plan asset allocation

	Pension Benefits						Other Postretirement Benefits
	2015		2014		2013		2015		2014		2013
	(in thousands)
Change in plan assets:
Fair value of plan assets at beginning of year	$	175,548		170,430		133,911		—		—		—
Actual return on plan assets		(11,479)		(6,149)		38,802		—		—		—
Employer contributions		20,000		20,000		17,000		156		146		(38)
Retiree contributions		—		—		—		349		381		321
Benefits paid		(10,184)		(8,733)		(19,283)		(505)		(527)		(283)
Fair value of plan assets at end of year	$	173,885		175,548		170,430		—		—		—
Funded status at end of year	$	(36,898)		(32,537)		(1,675)		(8,421)		(9,902)		(8,172)

	Pension Benefits						Other Postretirement Benefits
	2015		2014		2013		2015		2014		2013
	(in thousands, except percentage data)
Amounts recognized in the statement of financial position:
Current liabilities	$	—		—		—		(316)		(279)		(260)
Noncurrent liabilities		(36,898)		(32,537)		(1,675)		(8,105)		(9,623)		(7,912)
Net amount recognized at end of year	$	(36,898)		(32,537)		(1,675)		(8,421)		(9,902)		(8,172)
Amounts not yet reflected in net periodic benefit cost and included in accumulated other comprehensive income:
Transition obligation	$	(16)		(21)		(27)		—		—		—
Prior service credit (cost)		(720)		(1,179)		(1,822)		2		(17)		(72)
Accumulated gain (loss)		(88,882)		(75,681)		(30,602)		2,897		265		1,041
Accumulated other comprehensive income (loss)		(89,618)		(76,881)		(32,451)		2,899		248		969
Cumulative employer contributions in excess of (less than) net periodic benefit cost		52,720		44,344		30,776		(11,320)		(10,150)		(9,141)
Net amount recognized at end of year	$	(36,898)		(32,537)		(1,675)		(8,421)		(9,902)		(8,172)
Weighted average assumptions used to determine benefit obligation at December 31:
Discount rate		4.60%		4.13%		4.97%		4.44%		4.07%		4.94%
Rate of compensation increase		5.12%		5.12%		5.12%		Not applicable

Summary of entity's pension plan assets

Plan assets by category	Percentage of Plan Assets at December 31, 2015		Percentage of Plan Assets at December 31, 2014
Cash		24%		23%
Equity securities:
Domestic		53%		51%
International		15%		17%
Fixed income securities		5%		1%
Private equity		—		1%
Gold bullion		3%		7%
Total		100%		100%

Summary of entity's pension plan assets fair value

2015	Level 1		Level 2		Level 3		Total
	(in thousands)
Equity securities:
Domestic	$	92,037		—		—		92,037
International		25,822		—		—		25,822
Equity derivatives		—		280		—		280
Fixed income securities:
Mortgage-backed securities		—		11		—		11
U.S. treasuries		—		8,113		—		8,113
Gold bullion		5,226		—		—		5,226
Total investment securities		123,085		8,404		—		131,489
Cash and other								42,396
Total							$	173,885

2014	Level 1		Level 2		Level 3		Total
	(in thousands)
Equity securities:
Domestic	$	90,061		—		—		90,061
International		29,351		—		—		29,351
Equity derivatives		—		116		—		116
Fixed income securities:
Mortgage-backed securities		—		14		—		14
Corporate bond		—		—		1,884		1,884
Private equity		—		—		1,518		1,518
Gold bullion		12,209		—		—		12,209
Total investment securities		131,621		130		3,402		135,153
Cash and other								40,395
Total							$	175,548

Summary of the activity of plan assets categorized as Level 3

	2015		2014
	(in thousands)
Level 3 plan assets at beginning of year	$	3,402		4,019
Sales		(3,432)		—
Valuation change		30		(617)
Level 3 plan assets at end of year	$	—		3,402

Schedule of components of net periodic pension and other postretirement costs

	Pension Benefits						Other Postretirement Benefits
	2015		2014		2013		2015		2014		2013
	(in thousands)
Components of net periodic benefit cost:
Service cost	$	12,080		10,084		11,011		910		719		788
Interest cost		8,420		8,395		7,711		397		397		361
Expected return on plan assets		(14,510)		(14,016)		(11,185)		—		—		—
Actuarial (gain) loss amortization		5,171		1,496		4,567		—		(17)		—
Prior service cost amortization		459		468		555		19		55		55
Transition obligation amortization		5		5		5		—		—		—
Net periodic benefit cost	$	11,625		6,432		12,664		1,326		1,154		1,204

Schedule of weighted average assumptions used to determine net periodic cost and benefit obligation

	Pension Benefits						Other Postretirement Benefits
	2015		2014		2013		2015		2014		2013
Discount rate		4.13%		4.97%		4.22%		4.07%		4.94%		4.18%
Expected return on plan assets		7.75%		7.75%		7.75%		Not applicable
Rate of compensation increase		5.12%		5.12%		3.99%		Not applicable

Schedule of expected benefit payments to be paid

	Pension Benefits		Other Postretirement Benefits
	(in thousands)
2016	$	7,654		316
2017		8,274		343
2018		9,557		397
2019		10,518		454
2020		13,115		487
2021 through 2025		78,851		3,253
	$	127,969		5,250