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, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans
Change in plan assets:
Fair value of plan assets, beginning balance	$ 659,874
Fair value of plan assets, Ending Balance	583,659	$ 659,874
Other Postretirement Benefits
Change in benefit obligations:
Benefit obligation, beginning balance	56,647	56,141
Service cost	117	121	$ 115
Interest cost	2,168	2,340	2,483
Actuarial (gain) loss	(5,661)	2,008
Benefits paid	(2,881)	(3,963)
Benefit obligation, ending balance	50,390	56,647	56,141
Change in plan assets:
Fair value of plan assets, beginning balance	834	2,232
Actual return on plan assets	(253)	104
Employer contributions	2,300	2,461
Benefits paid	(2,881)	(3,963)
Fair value of plan assets, Ending Balance	0	834	2,232
Funded status	(50,390)	(55,813)
Current liabilities (accrued expenses)	(4,233)	(3,810)
Noncurrent liabilities (pension benefits)	(46,157)	(52,003)
Net pension liability	(50,390)	(55,813)
Prior service benefit	0	48
Net amount recognized	$ 0	$ 48
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	4.55%	3.99%
Rate of compensation increase	3.50%	3.50%
U.S. Plans | Pension Plans
Change in benefit obligations:
Benefit obligation, beginning balance	$ 685,963	$ 665,688
Service cost	1,043	985	1,028
Interest cost	26,804	28,614	30,514
Plan amendments	0	0
Actuarial (gain) loss	(36,844)	30,539
Benefits paid	(41,100)	(39,863)
Employee contributions	0	0
Foreign exchange (gain) loss	0	0
Settlements/curtailments	0	0
Other	0	0
Benefit obligation, ending balance	635,866	685,963	665,688
Change in plan assets:
Fair value of plan assets, beginning balance	580,396	538,082
Actual return on plan assets	(28,457)	80,613
Employer contributions	2,236	1,564
Benefits paid	(41,100)	(39,863)
Employee contributions	0	0
Foreign exchange (loss) gain	0	0
Settlements/curtailments	0	0
Other	0	0
Fair value of plan assets, Ending Balance	513,075	580,396	$ 538,082
Funded status	(122,791)	(105,567)
Current liabilities (accrued expenses)	(1,342)	(1,267)
Noncurrent liabilities (pension benefits)	(121,449)	(104,300)
Net pension liability	(122,791)	(105,567)
Prior service benefit	0	(60)
Net amount recognized	$ 0	$ (60)
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	4.59%	4.03%	4.43%	4.67%
Rate of compensation increase	0.00%	0.00%
Foreign Plans | Pension Plans
Change in benefit obligations:
Benefit obligation, beginning balance	$ 275,006	$ 246,280
Service cost	3,919	2,547	$ 3,133
Interest cost	5,144	5,128	6,570
Plan amendments	233	0
Actuarial (gain) loss	(17,885)	2,783
Benefits paid	(9,974)	(9,524)
Employee contributions	182	215
Foreign exchange (gain) loss	(12,632)	30,711
Settlements/curtailments	(3,628)	(3,065)
Other	(62)	(69)
Benefit obligation, ending balance	240,303	275,006	246,280
Change in plan assets:
Fair value of plan assets, beginning balance	79,478	68,875
Actual return on plan assets	(1,593)	6,260
Employer contributions	10,700	9,316
Benefits paid	(9,974)	(9,524)
Employee contributions	182	215
Foreign exchange (loss) gain	(4,519)	7,470
Settlements/curtailments	(3,628)	(3,065)
Other	(62)	(69)
Fair value of plan assets, Ending Balance	70,584	79,478	$ 68,875
Funded status	(169,719)	(195,528)
Current liabilities (accrued expenses)	(5,772)	(5,217)
Noncurrent liabilities (pension benefits)	(163,947)	(190,311)
Net pension liability	(169,719)	(195,528)
Prior service benefit	(409)	(269)
Net amount recognized	$ (409)	$ (269)
Weighted-average assumptions used to determine benefit obligations at December 31:
Discount rate	2.15%	1.94%	2.00%	2.76%
Rate of compensation increase	3.63%	3.18%