Retirement Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2019

Compensation And Retirement Disclosure [Abstract]

Changes in Benefit Obligations and Plan Assets

The following tables detail the changes in the benefit obligations and plan assets of the defined benefit plans for the years ended December 31, 2019 and 2018 as well as the funded status of the plans at each year end and the amounts recognized in the Company’s consolidated balance sheets. The Company uses a December 31 measurement date for all defined benefit pension plans and other postretirement benefit plans.

	2019			2018			2019			2018
(in thousands)	Pension Benefits						Other Post- Retirement Benefits
Change in benefit obligation
Benefit obligation at beginning of year	$	492,017		$	513,844		$	16,283		$	23,036
Service cost		10,981			12,414			95			120
Interest cost		18,843			16,762			621			621
Plan participants' contributions		—			—			547			628
Net actuarial (gain) loss		81,166			(30,796	)		733			(6,717	)
Benefits paid		(21,141	)		(20,207	)		(1,566	)		(1,405	)
Benefit obligation, end of year		581,866			492,017			16,713			16,283
Change in plan assets
Fair value of plan assets at beginning of year		542,618			564,365			—			—
Actual return on plan assets		130,745			(40,491	)		—			—
Employer contributions		101,165			40,138			1,019			777
Plan participants' contributions		—			—			547			628
Benefit payments		(21,141	)		(20,207	)		(1,566	)		(1,405	)
Expenses		(1,249	)		(1,187	)		—			—
Fair value of plan assets, end of year		752,138			542,618			—			—
Funded status at end of year - net asset (liability)	$	170,272		$	50,601		$	(16,713	)	$	(16,283	)
Amounts recognized in accumulated other    comprehensive loss
Unrecognized loss at beginning of year	$	149,470		$	102,978		$	(7,015	)	$	(732	)
Net actuarial loss (gain)		(13,218	)		46,492			1,646			(6,283	)
Unrecognized gain (loss) at end of year	$	136,252		$	149,470		$	(5,369	)	$	(7,015	)
Projected benefit obligation	$	581,866		$	492,017
Accumulated benefit obligation		550,005			467,300
Fair value of plan assets		752,138			542,618

Components of Net Periodic Benefits Cost

The following table shows net periodic benefit cost included in expense and the changes in the amounts recognized in AOCI during 2019, 2018, and 2017.

	Years Ended December 31,
	2019				2018				2017				2019				2018				2017
($ in thousands)	Pension Benefits												Other Post-Retirement Benefits
Net periodic benefit cost
Service cost	$		10,981		$		12,414		$		15,381		$		95		$		120		$		129
Interest cost			18,843				16,762				16,514				621				621				668
Expected return on plan assets			(45,199	)			(41,033	)			(37,632	)			—				—				—
Amortization of net loss/ prior service cost			10,087				5,423				5,554				(913	)			(434	)			(353	)
Net periodic benefit cost			(5,288	)			(6,434	)			(183	)			(197	)			307				444
Other changes in plan assets and benefit    obligations recognized in other    comprehensive income, before taxes
Net (loss) gain recognized during the year			(10,087	)			(5,423	)			(5,554	)			913				434				353
Net actuarial loss (gain)			(3,131	)			51,915				(7,378	)			733				(6,717	)			993
Total recognized in other comprehensive    income			(13,218	)			46,492				(12,932	)			1,646				(6,283	)			1,346
Total recognized in net periodic benefit    cost and other comprehensive income	$		(18,506	)	$		40,058		$		(13,115	)	$		1,449		$		(5,976	)	$		1,790
Discount rate for benefit obligations			3.14	%			4.14	%			3.57	%			3.11	%			4.10	%			3.52	%
Discount rate for net periodic benefit cost			4.14	%			3.57	%			4.10	%			4.10	%			3.52	%			3.95	%
Expected long-term return on plan assets			7.25	%			7.25	%			7.25	%		n/a				n/a				n/a
Rate of compensation increase		scaled *				scaled **				scaled **				n/a				n/a				n/a

* Graded scale, declining from 7.25% at age 20 to 2.25% at age 60

** Graded scale, declining from 7.00% at age 20 to 2.00% at age 60

Expected Plan Benefit Payments

The following table presents expected plan benefit payments over the ten years succeeding December 31, 2019:

(in thousands)	Pension		Post-Retirement		Total
2020	$	22,974	$	849	$	23,823
2021		24,016		888		24,904
2022		25,163		855		26,018
2023		26,130		876		27,006
2024		27,414		855		28,269
2025-2029		156,055		4,376		160,431
.	$	281,752	$	8,699	$	290,451

Assumed Health Care Cost Trend Rates

The following table illustrates the effect on the annual periodic postretirement benefit costs and postretirement benefit obligation of a 1% increase or 1% decrease in the assumed health care cost trend rates from the rates assumed at December 31, 2019:

	1% Decrease		Assumed		1% Increase
(in thousands)	in Rates		Rates		in Rates
Aggregated service and interest cost	$	642	$	715	$	806
Postretirement benefit obligation		15,031		16,712		18,780

Fair Values of Pension Plan Assets

For all investments, the plan attempts to use quoted market prices of identical assets on active exchanges, or Level 1 measurements. Where such quoted market prices are not available, the plan will use quoted prices for similar instruments or discounted cash flows to estimate the value, reported as Level 2

	December 31, 2019
Fair Value Measurements by Asset Category / Fund		Level 1			Level 2			Level 3		Total
(in thousands)
Cash and equivalents	$		2,574	$		—	$		—	$	2,574
Total cash and cash equivalents			2,574			—			—		2,574
Fixed income securities			23,450			45,951					69,401
Mutual fund-fixed income			34,652			—			—		34,652
Exchange Traded Fund (ETF)-fixed income			3,134								3,134
Total fixed income			61,236			45,951			—		107,187
Domestic and foreign stock			88,174						—		88,174
Mutual funds-equity			236,436			—			—		236,436
Total equity			324,610						—		324,610
Total assets at fair value			388,420			45,951			—		434,371
Common trust funds (fixed income)			—			—			—		258,572
Common trust fund (real assets)			—			—			—		59,195
Total	$		388,420	$		45,951	$		—	$	752,138

	December 31, 2018
Fair Value Measurements by Asset Category / Fund		Level 1			Level 2			Level 3			Total
(in thousands)
Cash and equivalents	$		8,643	$		—	$		—	$		8,643
Total cash and cash equivalents			8,643			—			—			8,643
Fixed income securities			19,856			97,025			—			116,881
Mutual fund-fixed income			31,556			—			145			31,701
Total fixed income			51,412			97,025			145			148,582
Domestic and foreign stock			80,813			6			—			80,819
Mutual funds-equity			150,466			—			—			150,466
Total equity			231,279			6			—			231,285
Total assets at fair value			291,334			97,031			145			388,510
Common trust funds (fixed income)			—			—			—			125,706
Common trust fund (real assets)			—			—			—			28,402
Total	$		291,334	$		97,031	$		145	$		542,618

Percentage and Target Allocations

The following table presents the percentage allocation of the plan assets by asset category and corresponding target allocations at December 31, 2019 and 2018.

	Plan Assets						Target Allocation
	at December 31,						at December 31,
Asset category	2019			2018			2019	2018
Cash and equivalents		0	%		1	%	0 - 5%	0 - 5%
Fixed income securities		49			51		41 - 57%	35 - 63%
Equity securities		43			43		35 - 51%	35 - 51%
Real assets		8			5		0 - 12%	0 - 12%
		100	%		100	%