Pensions and Other Postretirement Benefits (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) Plan	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Amounts recognized in balance sheet associated with retirement benefit plans [Abstract]
Included in other assets	$ 356	$ 347
Pension and Other Postretirement Defined Benefit Plans, Current Liabilities	(8,147)	(8,503)
Accrued pension and other postretirement costs	(260,984)	(281,701)
Total actuarial items	82,986	96,944
Components of actuarial items [Abstract]
Total actuarial items	82,986	96,944
Components of net periodic pension cost [Abstract]
Curtailment and settlement losses (gains)	0	0	$ 79,321
Amounts that will be amortized from accumulated other comprehensive loss into net periodic pension cost during next fiscal year	$ 6,300
Other postretirement benefits [Abstract]
Number of unfunded non-pension postretirement plans | Plan	2
Number of European subsidiaries with unfunded non-pension postretirement plans | Plan	2
Other retirement obligations [Abstract]
Company's matching expense for 401(k) savings plans	$ 6,353	5,843	5,039
Defined Benefit Pension [Member] | Domestic Plan [Member]
Change in benefit obligation [Roll forward]
Benefit obligation at beginning of year	39,917	38,914
Service cost	0	0	0
Interest cost	1,484	1,643	11,788
Plan amendments and initiations	0	0
Transfer from equity affiliate (liabilities)	0	0
Actuarial (gains) losses	(1,431)	1,149
Benefits paid	(1,801)	(1,789)
Curtailments and settlements	0	0
Currency translation	0	0
Benefit obligation at end of year	38,169	39,917	38,914
Change in plan assets [Roll forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Transfer from Equity Affiliate (assets)	0	0
Company contributions	1,801	1,789
Benefits paid	(1,801)	(1,789)
Curtailments and settlements	0	0
Currency translation	0	0
Fair value of plan assets at end of year	0	0	0
Funded status at end of year	(38,169)	(39,917)
Amounts recognized in balance sheet associated with retirement benefit plans [Abstract]
Included in other assets	0	0
Pension and Other Postretirement Defined Benefit Plans, Current Liabilities	(35)	(37)
Accrued pension and other postretirement costs	(38,134)	(39,880)
Total actuarial items	5,501	7,731
Total	(32,668)	(32,186)
Components of actuarial items [Abstract]
Unrecognized net actuarial loss (gain)	4,717	6,804
Unamortized prior service (credit) cost	784	927
Total actuarial items	5,501	7,731
Projected and accumulated benefit obligations [Abstract]
Accumulated benefit obligation, all plans	38,169	39,917
Plans for which the accumulated benefit obligation exceeds plan assets [Abstract]
Projected benefit obligation	38,169	39,917
Accumulated benefit obligation	38,169	39,917
Fair value of plan assets	0	0
Components of net periodic pension cost [Abstract]
Net service cost	0	0	0
Interest cost	1,484	1,643	11,788
Expected return on plan assets	0	0	(11,302)
Amortization of actuarial losses	656	587	6,513
Amortization of prior service (credit) cost	144	144	144
Curtailment and settlement losses (gains)	0	0	79,321
Net periodic benefit cost	$ 2,284	$ 2,374	86,464
Weighted average assumptions used to calculate benefit obligations [Abstract]
Discount rate (in hundredths)	4.50%	3.75%
Rate of compensation increase (in hundredths)	0.00%	0.00%
Weighted average assumptions used calculating net periodic benefit cost [Abstract]
Discount rate (in hundredths)	3.75%	4.25%
Rate of compensation increase (in hundredths)	0.00%	0.00%
Expected return on plan assets (in hundredths)	0.00%	0.00%
Estimated future benefit payments [Abstract]
2019	$ 1,859
2020	1,829
2021	8,364
2022	3,153
2023	3,159
2024-2028	17,122
Defined Benefit Pension [Member] | Foreign Plan [Member]
Change in benefit obligation [Roll forward]
Benefit obligation at beginning of year	291,162	$ 266,427
Service cost	3,822	3,725	3,291
Interest cost	4,793	4,866	5,475
Plan amendments and initiations	125	686
Transfer from equity affiliate (liabilities)	0	0
Actuarial (gains) losses	(1,311)	3,019
Benefits paid	(14,397)	(17,921)
Curtailments and settlements	0	0
Currency translation	(12,236)	30,360
Benefit obligation at end of year	271,958	291,162	266,427
Change in plan assets [Roll forward]
Fair value of plan assets at beginning of year	70,605	66,090
Actual return on plan assets	1,412	1,608
Transfer from Equity Affiliate (assets)	0	0
Company contributions	16,105	16,120
Benefits paid	(14,397)	(17,921)
Curtailments and settlements	0	0
Currency translation	(2,905)	4,708
Fair value of plan assets at end of year	70,820	70,605	66,090
Funded status at end of year	(201,138)	(220,557)
Amounts recognized in balance sheet associated with retirement benefit plans [Abstract]
Included in other assets	356	347
Pension and Other Postretirement Defined Benefit Plans, Current Liabilities	(7,228)	(7,308)
Accrued pension and other postretirement costs	(194,266)	(213,596)
Total actuarial items	76,698	88,398
Total	(124,440)	(132,159)
Components of actuarial items [Abstract]
Unrecognized net actuarial loss (gain)	76,254	87,896
Unamortized prior service (credit) cost	444	502
Total actuarial items	76,698	88,398
Projected and accumulated benefit obligations [Abstract]
Accumulated benefit obligation, all plans	258,244	270,914
Plans for which the accumulated benefit obligation exceeds plan assets [Abstract]
Projected benefit obligation	247,066	277,615
Accumulated benefit obligation	235,167	262,779
Fair value of plan assets	45,818	57,727
Components of net periodic pension cost [Abstract]
Net service cost	3,822	3,725	3,291
Interest cost	4,793	4,866	5,475
Expected return on plan assets	(1,889)	(2,072)	(2,117)
Amortization of actuarial losses	6,196	6,179	4,733
Amortization of prior service (credit) cost	318	150	261
Curtailment and settlement losses (gains)	1,111	1,360	841
Net periodic benefit cost	$ 14,351	$ 14,208	12,484
Weighted average assumptions used to calculate benefit obligations [Abstract]
Discount rate (in hundredths)	1.96%	1.80%
Rate of compensation increase (in hundredths)	2.17%	2.10%
Weighted average assumptions used calculating net periodic benefit cost [Abstract]
Discount rate (in hundredths)	1.80%	1.76%
Rate of compensation increase (in hundredths)	2.10%	2.12%
Expected return on plan assets (in hundredths)	2.95%	2.90%
Estimated future benefit payments [Abstract]
2019	$ 18,612
2020	15,113
2021	15,319
2022	17,300
2023	16,327
2024-2028	81,505
Other Postretirement Benefits [Member] | Domestic Plan [Member]
Change in benefit obligation [Roll forward]
Benefit obligation at beginning of year	7,633	$ 7,647
Service cost	137	131	126
Interest cost	273	311	340
Actuarial (gains) losses	(344)	257
Benefits paid	(705)	(713)
Curtailments and settlements	0	0
Currency translation	0	0
Benefit obligation at end of year	6,994	7,633	7,647
Change in plan assets [Roll forward]
Fair value of plan assets at beginning of year	0
Benefits paid	(705)	(713)
Fair value of plan assets at end of year	0	0
Funded status at end of year	(6,994)	(7,633)
Amounts recognized in balance sheet associated with retirement benefit plans [Abstract]
Pension and Other Postretirement Defined Benefit Plans, Current Liabilities	(703)	(705)
Accrued pension and other postretirement costs	(6,291)	(6,928)
Total actuarial items	(1,257)	(1,101)
Total	(8,251)	(8,734)
Components of actuarial items [Abstract]
Unrecognized net actuarial loss (gain)	(1,257)	(953)
Unamortized prior service (credit) cost	0	(148)
Total actuarial items	(1,257)	(1,101)
Components of net periodic pension cost [Abstract]
Net service cost	137	131	126
Interest cost	273	311	340
Amortization of actuarial losses	(39)	(93)	(30)
Amortization of prior service (credit) cost	(148)	(837)	(837)
Net periodic benefit cost	$ 223	$ (488)	(401)
Weighted average assumptions used to calculate benefit obligations [Abstract]
Discount rate (in hundredths)	4.50%	3.75%
Rate of compensation increase (in hundredths)	0.00%	0.00%
Weighted average assumptions used calculating net periodic benefit cost [Abstract]
Discount rate (in hundredths)	3.75%	4.25%
Rate of compensation increase (in hundredths)	0.00%	0.00%
Estimated future benefit payments [Abstract]
2019	$ 703
2020	671
2021	661
2022	633
2023	294
2024-2028	2,244
Other Postretirement Benefits [Member] | Foreign Plan [Member]
Change in benefit obligation [Roll forward]
Benefit obligation at beginning of year	7,898	$ 6,625
Service cost	288	273	268
Interest cost	114	103	143
Actuarial (gains) losses	327	312
Benefits paid	(303)	(349)
Curtailments and settlements	0	0
Currency translation	(371)	934
Benefit obligation at end of year	7,953	7,898	6,625
Change in plan assets [Roll forward]
Fair value of plan assets at beginning of year	0
Benefits paid	(303)	(349)
Fair value of plan assets at end of year	0	0
Funded status at end of year	(7,953)	(7,898)
Amounts recognized in balance sheet associated with retirement benefit plans [Abstract]
Pension and Other Postretirement Defined Benefit Plans, Current Liabilities	(181)	(453)
Accrued pension and other postretirement costs	(7,772)	(7,445)
Total actuarial items	2,044	1,916
Total	(5,909)	(5,982)
Components of actuarial items [Abstract]
Unrecognized net actuarial loss (gain)	2,044	1,916
Unamortized prior service (credit) cost	0	0
Total actuarial items	2,044	1,916
Components of net periodic pension cost [Abstract]
Net service cost	288	273	268
Interest cost	114	103	143
Amortization of actuarial losses	105	76	68
Amortization of prior service (credit) cost	0	0	0
Net periodic benefit cost	$ 507	$ 452	$ 479
Weighted average assumptions used to calculate benefit obligations [Abstract]
Discount rate (in hundredths)	1.60%	1.50%
Rate of compensation increase (in hundredths)	3.18%	2.88%
Weighted average assumptions used calculating net periodic benefit cost [Abstract]
Discount rate (in hundredths)	1.50%	1.50%
Rate of compensation increase (in hundredths)	2.88%	2.58%
Estimated future benefit payments [Abstract]
2019	$ 181
2020	387
2021	337
2022	776
2023	281
2024-2028	3,183
Other Retirement Obligations [Member]
Amounts recognized in balance sheet associated with retirement benefit plans [Abstract]
Accrued pension and other postretirement costs	(14,521)	$ (13,852)
Deferred Compensation [Member]
Defined benefit pension plans [Abstract]
Assets held in trust	18,162	18,958
Non-qualified Pension Plans [Member]
Defined benefit pension plans [Abstract]
Assets held in trust	22,409	24,505
Dr. Felix Zandman [Member] | Non-qualified Pension Plans [Member]
Defined benefit pension plans [Abstract]
Assets held in trust	1,199	$ 1,789
Deferred compensation arrangement, annual retirement benefit to surviving spouse	$ 614