Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2017

Retirement Benefits [Abstract]

Schedule of Changes in Projected Benefit Obligations [Table Text Block]

A December 31 measurement date is used for all of the defined benefit and postretirement plans. The status of these plans as of December 31, 2017 and 2016 is summarized below (dollars in thousands):

	December 31,
	Pension Benefits						Other Benefits
	2017			2016			2017			2016
Change in benefit obligation:
Benefit obligation at beginning of year	$	161,955		$	142,239		$	60,524		$	63,307
Service cost	10,686			10,319			2,543			2,883
Interest Cost	5,326			4,790			2,118			2,259
Participant contributions	—			—			354			305
Amendments(1)	159			—			—			(13,743		)
Actuarial (gains) losses	11,336			9,973			5,510			6,228
Settlement (gains) losses	(438		)	258			—			—
Settlements	(12,907		)	(3,152		)	—			—
Benefits paid	(5,974		)	(3,047		)	(851		)	(715		)
Foreign exchange translations and other adjustments	2,000			575			—			—
Benefit obligation at end of year	$	172,143		$	161,955		$	70,198		$	60,524

Schedule of Changes in Fair Value of Plan Assets [Table Text Block]

	December 31,
	Pension Benefits						Other Benefits
	2017			2016			2017			2016
Change in plan assets:
Fair value of plan assets at beginning of year	$	84,770		$	68,435		$	—		$	—
Actual return on plan assets	14,481			6,584			—			—
Employer contributions	22,866			15,950			497			410
Participant contributions	—			—			354			305
Disbursement for settlements	(12,907		)	(3,152		)	—			—
Benefits paid and expenses	(5,974		)	(3,047		)	(851		)	(715		)
Fair value of plan assets at end of year	$	103,236		$	84,770		$	—		$	—
Funded status at end of year	$	(68,907	)	$	(77,185	)	$	(70,198	)	$	(60,524	)

Schedule of Net Funded Status [Table Text Block]

	December 31,
	Qualified Plans						Non-Qualified Plans(1)						Total
	2017			2016			2017			2016			2017			2016
Aggregate fair value of plan assets	$	103,236		$	84,770		$	—		$	—		$	103,236		$	84,770
Aggregate projected benefit obligations	107,072			96,418			65,071			65,537			172,143			161,955
Under funded	$	(3,836	)	$	(11,648	)	$	(65,071	)	$	(65,537	)	$	(68,907	)	$	(77,185	)

(1) For non-qualified plans, there are no required funding levels.

Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]

	December 31,
	Pension Benefits				Other Benefits
	2017		2016		2017			2016
Amounts recognized in accumulated other comprehensive income:
Net actuarial loss	$	40,058	$	46,119	$	35,672		$	32,156
Net prior service cost (credit)	804		703		(11,806		)	(13,121		)
Total	$	40,862	$	46,822	$	23,866		$	19,035

Schedule Of Projected Benefit Obligations In Excess Of Fair Value Of Plan Assets [Table Text Block]

The following table presents information for qualified and non-qualified pension plans with a projected benefit obligation in excess of plan assets as of December 31, 2017 and 2016 (dollars in thousands):

	2017		2016
Projected benefit obligation	$	172,143	$	161,955
Fair value of plan assets	103,236		84,770

Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]

The following table presents information for pension plans with an accumulated benefit obligation in excess of plan assets as of December 31, 2017 and 2016 (dollars in thousands):

	2017		2016
Accumulated benefit obligation	$	169,705	$	158,580
Fair value of plan assets	103,236		84,770

Schedule of Defined Benefit Plan Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]

The components of net periodic benefit cost, included in other operating expenses on the consolidated statements of income, and other changes in plan assets and benefit obligations recognized in other comprehensive income were as follows (dollars in thousands):

	Pension Benefits									Other Benefits
	2017			2016			2015			2017			2016			2015
Net periodic benefit cost:
Service cost	$	10,686		$	10,319		$	9,222		$	2,543		$	2,883		$	4,062
Interest cost	5,326			4,790			5,035			2,118			2,259			2,572
Expected return on plan assets	(6,215		)	(5,138		)	(4,897		)	—			—			—
Amortization of prior actuarial losses	4,382			4,323			3,429			1,992			1,827			2,465
Amortization of prior service cost (credit)	344			294			309			(1,315		)	(622		)	—
Settlements	4,785			1,026			—			—			—			—
Net periodic benefit cost	19,308			15,614			13,098			5,338			6,347			9,099
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net actuarial (gains) losses	2,633			8,785			5,774			5,507			6,228			(2,729		)
Amortization of actuarial (gains) losses	(4,382		)	(4,323		)	(3,429		)	(1,992		)	(1,827		)	(2,465		)
Amortization of prior service cost (credit)	(344		)	(294		)	(309		)	1,315			622			—
Settlements	(4,785		)	(1,026		)	—			—			—			—
Prior service cost (credit) (1)	159			—			—			—			(13,743		)	—
Foreign exchange translations and other adjustments	759			707			(1,797		)	—			—			—
Total recognized in other comprehensive income	(5,960		)	3,849			239			4,830			(8,720		)	(5,194		)
Total recognized in net periodic benefit cost and other comprehensive income	$	13,348		$	19,463		$	13,337		$	10,168		$	(2,373	)	$	3,905

Schedule of Expected Benefit Payments [Table Text Block]

The following benefit payments, which reflect expected future service as appropriate, are expected to be paid (dollars in thousands):

	Pension Benefits		Other Benefits
2018	$	9,315	$	1,238
2019	9,765		1,495
2020	10,885		1,842
2021	11,102		2,188
2022	13,184		2,521
2023-2027	69,285		18,205

Schedule of Assumptions Used [Table Text Block]

Weighted average assumptions used to determine the accumulated benefit obligation and net benefit cost or income were as follows:

	Pension Benefits						Other Benefits
	2017		2016		2015		2017		2016		2015
Discount rate used to determine benefit obligation	3.40	%	3.80	%	3.99	%	3.56	%	4.10	%	4.43	%
Discount rate used to determine net benefit cost or income	3.81	%	3.95	%	3.77	%	4.10	%	4.43	%	4.05	%
Expected long-term rate of return on plan assets	7.35	%	7.35	%	7.35	%	—	%	—	%	—	%
Rate of compensation increases	4.16	%	4.08	%	4.08	%	—	%	—	%	—	%

Schedule of Health Care Cost Trend Rates [Table Text Block]

The assumed health care cost trend rates used in measuring the accumulated non-pension post-retirement benefit obligation were as follows:

	December 31,
	2017	2016
Pre-Medicare eligible claims	9% down to 5% in 2024	10% down to 5% in 2024
Medicare eligible claims	9% down to 5% in 2024	10% down to 5% in 2024

Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]

A one-percentage point change in assumed health care cost trend rates would have the following effects (dollars in thousands):

	One Percent Increase		One Percent Decrease
Effect on total of service and interest cost components	$	7,941	$	(7,104	)
Effect on accumulated postretirement benefit obligation	$	447	$	(359	)

Schedule of Allocation of Plan Assets [Table Text Block]

The fair values of the Company’s qualified pension plan assets as of December 31, 2017 and 2016 are summarized below (dollars in thousands):

	December 31, 2017
			Fair Value Measurement Using:
	Total		Level 1		Level 2		Level 3
Mutual Funds(1)	$	103,106	$	103,106	$	—	$	—
Cash	130		130		—		—
Total	$	103,236	$	103,236	$	—	$	—

(1) Mutual funds were invested 27% in U.S. equity funds, 36% in U.S. fixed income funds, 22% in non-U.S. equity funds and 15% in other.

	December 31, 2016
			Fair Value Measurement Using:
	Total		Level 1		Level 2		Level 3
Mutual Funds(2)	$	84,671	$	84,671	$	—	$	—
Cash	99		99		—		—
Total	$	84,770	$	84,770	$	—	$	—

(2) Mutual funds were invested 28% in U.S. equity funds, 37% in U.S. fixed income funds, 20% in non-U.S. equity funds and 15% in other.