Pension Plans and Other Postretirement Benefits Reconciliation of Benefit Obligations, Plan Assets and Funded Status of Plans, as well as Summary of Significant Assumptions for Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plans
Change in plan assets:
Fair value of plan assets, beginning balance	$ 638,149
Fair value of plan assets, Ending Balance	683,469	$ 638,149
Other Postretirement Benefits
Change in benefit obligations:
Benefit obligation, beginning balance	55,089	50,390
Service cost	105	98	$ 117
Interest cost	1,871	2,197	2,168
Actuarial loss	(2,571)	5,445
Benefits paid	(3,151)	(3,041)
Benefit obligation, ending balance	51,343	55,089	50,390
Change in plan assets:
Fair value of plan assets, beginning balance	0	0
Defined Benefit Plan, Plan Assets, Contributions by Employer	3,151	3,041
Benefits paid	(3,151)	(3,041)
Fair value of plan assets, Ending Balance	0	0	0
Funded status	(51,343)	(55,089)
Current liabilities (accrued expenses)	(3,268)	(4,190)
Noncurrent liabilities (pension benefits)	(48,075)	(50,899)
Net pension liability	$ (51,343)	$ (55,089)
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	2.49%	3.53%
Rate of compensation increase	3.50%	3.50%
U.S. Plans | Pension Plans
Change in benefit obligations:
Benefit obligation, beginning balance	$ 678,720	$ 635,866
Service cost	849	730	1,043
Interest cost	23,402	28,199	26,804
Plan amendments	0	0
Actuarial loss	79,780	56,108
Benefits paid	(41,800)	(42,183)
Employee contributions	0	0
Foreign exchange loss (gain)	0	0
Settlements/curtailments	0	0
Other	0	0
Benefit obligation, ending balance	740,951	678,720	635,866
Change in plan assets:
Fair value of plan assets, beginning balance	556,683	513,075
Actual return on plan assets	75,715	82,926
Defined Benefit Plan, Plan Assets, Contributions by Employer	3,630	2,865
Benefits paid	(41,800)	(42,183)
Employee contributions	0	0
Foreign exchange gain	0	0
Settlements/curtailments	0	0
Other	0	0
Fair value of plan assets, Ending Balance	594,228	556,683	$ 513,075
Funded status	(146,723)	(122,037)
Current liabilities (accrued expenses)	(1,217)	(1,224)
Noncurrent liabilities (pension benefits)	(145,506)	(120,813)
Net pension liability	(146,723)	(122,037)
Prior service benefit	0	0
Net amount recognized	$ 0	$ 0
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	2.50%	3.56%	4.59%	4.03%
Rate of compensation increase	0.00%	0.00%
Foreign Plans | Pension Plans
Change in benefit obligations:
Benefit obligation, beginning balance	$ 258,374	$ 240,303
Service cost	4,000	3,680	$ 3,919
Interest cost	3,357	4,998	5,144
Plan amendments	593	0
Actuarial loss	19,571	21,588
Benefits paid	(9,905)	(10,088)
Employee contributions	101	133
Foreign exchange loss (gain)	19,858	(1,772)
Settlements/curtailments	(5,866)	(398)
Other	302	(70)
Benefit obligation, ending balance	290,385	258,374	240,303
Change in plan assets:
Fair value of plan assets, beginning balance	81,466	70,584
Actual return on plan assets	8,173	9,417
Defined Benefit Plan, Plan Assets, Contributions by Employer	9,653	10,572
Benefits paid	(9,905)	(10,088)
Employee contributions	101	133
Foreign exchange gain	4,110	1,316
Settlements/curtailments	(4,279)	(398)
Other	(78)	(70)
Fair value of plan assets, Ending Balance	89,241	81,466	$ 70,584
Funded status	(201,144)	(176,908)
Current liabilities (accrued expenses)	(5,832)	(5,648)
Noncurrent liabilities (pension benefits)	(195,312)	(171,260)
Net pension liability	(201,144)	(176,908)
Prior service benefit	(433)	224
Net amount recognized	$ (433)	$ 224
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	0.86%	1.33%	2.15%	1.94%
Rate of compensation increase	3.82%	3.72%