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, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans
Change in plan assets:
Fair value of plan assets, beginning balance	$ 606,957
Fair value of plan assets, Ending Balance	659,874	$ 606,957
Other Postretirement Benefits
Change in benefit obligations:
Benefit obligation, beginning balance	56,141	56,499
Service cost	121	115	$ 137
Interest cost	2,340	2,483	2,573
Actuarial loss	2,008	1,529
Benefits paid	(3,963)	(4,485)
Benefit obligation, ending balance	56,647	56,141	56,499
Change in plan assets:
Fair value of plan assets, beginning balance	2,232	3,292
Actual return on plan assets	104	442
Employer contributions	2,461	2,983
Benefits paid	(3,963)	(4,485)
Fair value of plan assets, Ending Balance	834	2,232	3,292
Funded status	(55,813)	(53,909)
Current liabilities (accrued expenses)	(3,810)	(3,371)
Noncurrent liabilities (pension benefits)	(52,003)	(50,538)
Net pension liability	(55,813)	(53,909)
Prior service benefit	48	143
Net amount recognized	$ 48	$ 143
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	3.99%	4.35%
Rate of compensation increase	3.50%	3.50%
U.S. Plans | Pension Plans
Change in benefit obligations:
Benefit obligation, beginning balance	$ 665,688	$ 682,839
Service cost	985	1,028	1,233
Interest cost	28,614	30,514	30,235
Actuarial loss	30,539	7,357
Benefits paid	(39,863)	(56,050)
Divestitures	0	0
Employee contributions	0	0
Foreign exchange loss (gain)	0	0
Settlements/curtailments	0	0
Other	0	0
Benefit obligation, ending balance	685,963	665,688	682,839
Change in plan assets:
Fair value of plan assets, beginning balance	538,082	555,084
Actual return on plan assets	80,613	37,725
Employer contributions	1,564	1,323
Benefits paid	(39,863)	(56,050)
Employee contributions	0	0
Foreign exchange gain (loss)	0	0
Settlements/curtailments	0	0
Other	0	0
Fair value of plan assets, Ending Balance	580,396	538,082	555,084
Funded status	(105,567)	(127,606)
Current liabilities (accrued expenses)	(1,267)	(1,100)
Noncurrent liabilities (pension benefits)	(104,300)	(126,506)
Net pension liability	(105,567)	(127,606)
Prior service benefit	(60)	(136)
Net amount recognized	$ (60)	$ (136)
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	4.03%	4.43%
Rate of compensation increase	0.00%	0.00%
Foreign Plans | Pension Plans
Change in benefit obligations:
Benefit obligation, beginning balance	$ 246,280	$ 245,747
Service cost	2,547	3,133	3,909
Interest cost	5,128	6,570	6,405
Actuarial loss	2,783	28,083
Benefits paid	(9,524)	(9,793)
Divestitures	0	(6,372)
Employee contributions	215	245
Foreign exchange loss (gain)	30,711	(21,724)
Settlements/curtailments	(3,065)	(427)
Other	(69)	818
Benefit obligation, ending balance	275,006	246,280	245,747
Change in plan assets:
Fair value of plan assets, beginning balance	68,875	64,911
Actual return on plan assets	6,260	12,534
Employer contributions	9,316	10,911
Benefits paid	(9,524)	(9,793)
Employee contributions	215	245
Foreign exchange gain (loss)	7,470	(10,492)
Settlements/curtailments	(3,065)	0
Other	(69)	559
Fair value of plan assets, Ending Balance	79,478	68,875	$ 64,911
Funded status	(195,528)	(177,405)
Current liabilities (accrued expenses)	(5,217)	(5,216)
Noncurrent liabilities (pension benefits)	(190,311)	(172,189)
Net pension liability	(195,528)	(177,405)
Prior service benefit	(269)	(322)
Net amount recognized	$ (269)	$ (322)
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	1.94%	2.00%
Rate of compensation increase	3.18%	3.18%