Pension and Other Postretirement Benefits - Funded Status Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	$ 150,586
Fair Value of Plan Assets at End of Year	144,241	$ 150,586
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current Asset	3,656	1,184
Current Liabilities	(1,211)	(1,108)
Non-current Liabilities	(32,360)	(35,548)
Domestic [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	51,964
Fair Value of Plan Assets at End of Year	49,415	51,964
Domestic [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	62,977	67,254
Service Cost	383	337	$ 298
Interest Cost	1,847	1,932	2,114
Employee Contributions	0	0
Benefits Paid	(4,330)	(4,031)
Plan Settlements	0	(4,341)
Plan Expense and Premiums Paid	0	0
Actuarial (gain) Loss	(2,143)	1,826
Translation Difference and Other	0	0
Benefit Obligation at End of Year	58,734	62,977	67,254
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	51,964	49,197
Actual Return on Plan Assets	457	6,865
Employer Contributions	1,574	4,574
Employee Contributions	0	0
Benefits Paid	(4,330)	(4,031)
Plan Settlements	0	(4,341)
Plan Expenses and Premiums Paid	(250)	(300)
Translation Difference	0	0
Fair Value of Plan Assets at End of Year	49,415	51,964	49,197
Defined Benefit Plan, Funded Status of Plan	(9,319)	(11,013)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current Asset	3,656	1,184
Current Liabilities	(559)	(560)
Non-current Liabilities	(12,416)	(11,637)
Net Amount Recognized	(9,319)	(11,013)
Amounts Not Yet Reflected in Net Periodic Benefit Costs and Included in Accumulated Other Comprehensive Income (Loss) [Abstract]
Prior Service credit (cost)	0	(59)
Accumulated Loss	(25,310)	(27,133)
Accumulated Other Comprehensive Loss ("AOCI")	(25,310)	(27,192)
Cumulative Employer Contributions In Excess Of (or Below) Net Periodic Benefit Cost	15,991	16,179
Net Amount Recognized	(9,319)	(11,013)
Domestic [Member] | Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	4,729	4,730
Service Cost	7	8	10
Interest Cost	130	144	142
Employee Contributions	0	0
Benefits Paid	(317)	(448)
Plan Settlements	0	0
Plan Expense and Premiums Paid	0	0
Actuarial (gain) Loss	(443)	295
Translation Difference and Other	0	0
Benefit Obligation at End of Year	4,106	4,729	4,730
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	0	0
Actual Return on Plan Assets	0	0
Employer Contributions	317	448
Employee Contributions	0	0
Benefits Paid	(317)	(448)
Plan Settlements	0	0
Plan Expenses and Premiums Paid	0	0
Translation Difference	0	0
Fair Value of Plan Assets at End of Year	0	0	0
Defined Benefit Plan, Funded Status of Plan	(4,106)	(4,729)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current Asset	0	0
Current Liabilities	(446)	(459)
Non-current Liabilities	(3,660)	(4,270)
Net Amount Recognized	(4,106)	(4,729)
Amounts Not Yet Reflected in Net Periodic Benefit Costs and Included in Accumulated Other Comprehensive Income (Loss) [Abstract]
Prior Service credit (cost)	0	0
Accumulated Loss	(338)	(823)
Accumulated Other Comprehensive Loss ("AOCI")	(338)	(823)
Cumulative Employer Contributions In Excess Of (or Below) Net Periodic Benefit Cost	(3,768)	(3,906)
Net Amount Recognized	(4,106)	(4,729)
Foreign [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	98,622
Fair Value of Plan Assets at End of Year	94,826	98,622
Foreign [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	118,352	103,491
Service Cost	3,426	3,219	2,378
Interest Cost	2,254	2,066	2,314
Employee Contributions	73	68
Benefits Paid	(1,639)	(2,503)
Plan Settlements	(10)	0
Plan Expense and Premiums Paid	(161)	(210)
Actuarial (gain) Loss	(5,561)	(1,164)
Translation Difference and Other	(5,418)	13,385
Benefit Obligation at End of Year	111,316	118,352	103,491
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	98,622	86,844
Actual Return on Plan Assets	(2,670)	116
Employer Contributions	5,269	2,867
Employee Contributions	73	68
Benefits Paid	(1,639)	(2,503)
Plan Settlements	(10)	0
Plan Expenses and Premiums Paid	(161)	(210)
Translation Difference	(4,658)	11,440
Fair Value of Plan Assets at End of Year	94,826	98,622	86,844
Defined Benefit Plan, Funded Status of Plan	(16,490)	(19,730)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current Asset	0	0
Current Liabilities	(206)	(89)
Non-current Liabilities	(16,284)	(19,641)
Net Amount Recognized	(16,490)	(19,730)
Amounts Not Yet Reflected in Net Periodic Benefit Costs and Included in Accumulated Other Comprehensive Income (Loss) [Abstract]
Prior Service credit (cost)	1,497	1,744
Accumulated Loss	(20,089)	(22,598)
Accumulated Other Comprehensive Loss ("AOCI")	(18,592)	(20,854)
Cumulative Employer Contributions In Excess Of (or Below) Net Periodic Benefit Cost	2,102	1,124
Net Amount Recognized	(16,490)	(19,730)
Pension Plans, Defined Benefit [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	181,329	170,745
Service Cost	3,809	3,556	2,676
Interest Cost	4,101	3,998	4,428
Employee Contributions	73	68
Benefits Paid	(5,969)	(6,534)
Plan Settlements	(10)	(4,341)
Plan Expense and Premiums Paid	(161)	(210)
Actuarial (gain) Loss	(7,704)	662
Translation Difference and Other	(5,418)	13,385
Benefit Obligation at End of Year	170,050	181,329	170,745
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	150,586	136,041
Actual Return on Plan Assets	(2,213)	6,981
Employer Contributions	6,843	7,441
Employee Contributions	73	68
Benefits Paid	(5,969)	(6,534)
Plan Settlements	(10)	(4,341)
Plan Expenses and Premiums Paid	(411)	(510)
Translation Difference	(4,658)	11,440
Fair Value of Plan Assets at End of Year	144,241	150,586	$ 136,041
Defined Benefit Plan, Funded Status of Plan	(25,809)	(30,743)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current Asset	3,656	1,184
Current Liabilities	(765)	(649)
Non-current Liabilities	(28,700)	(31,278)
Net Amount Recognized	(25,809)	(30,743)
Amounts Not Yet Reflected in Net Periodic Benefit Costs and Included in Accumulated Other Comprehensive Income (Loss) [Abstract]
Prior Service credit (cost)	1,497	1,685
Accumulated Loss	(45,399)	(49,731)
Accumulated Other Comprehensive Loss ("AOCI")	(43,902)	(48,046)
Cumulative Employer Contributions In Excess Of (or Below) Net Periodic Benefit Cost	18,093	17,303
Net Amount Recognized	$ (25,809)	$ (30,743)