Pension and Other Postretirement Benefits - Funded Status Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Employee Contributions	$ 73	$ 73
Benefits Paid	(11,225)	(9,866)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	315,649	144,241
Actual Return on Plan Assets	31,126	24,121
Employer Contributions	9,214	6,310
Employee Contributions	73	73
Plan Settlements	(55,810)	(1,087)
Benefits Paid	(11,225)	(9,866)
Plan Expenses and Premiums Paid	(633)	(629)
Transfer In of Business Acquisition	0	146,987
Translation Difference	13,876	5,499
Fair Value of Plan Assets at End of Year	302,270	315,649	$ 144,241
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current Asset	6,748	0
Current Liabilities	(1,466)	(3,405)
Non-current Liabilities	(63,890)	(56,828)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	371,616	170,050
Service Cost	4,831	3,941	3,809
Interest Cost	6,339	6,359	4,101
Employee Contributions	73	73
Effect of Plan Amendments	50	30
Plan Settlements	(55,810)	(1,087)
Defined Benefit Plan, Curtailments	(2,324)	0
Benefits Paid	(11,225)	(9,866)
Plan Expenses and Premiums Paid	(135)	(129)
Transfer In of Business Acquisition	0	172,072
Actuarial (gain) Loss	29,248	24,478
Translation Difference and Other	14,981	5,695
Benefit Obligation at End of Year	357,644	371,616	170,050
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	315,649
Employee Contributions	73	73
Benefits Paid	(11,225)	(9,866)
Fair Value of Plan Assets at End of Year	91,555	315,649
Defined Benefit Plan, Funded Status of Plan	(55,374)	(55,967)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current Asset	6,748	0
Current Liabilities	(1,180)	(2,979)
Non-current Liabilities	(60,942)	(52,988)
Net Amount Recognized	(55,374)	(55,967)
Amounts Not Yet Reflected in Net Periodic Benefit Costs and Included in Accumulated Other Comprehensive Income (Loss) [Abstract]
Prior Service credit (cost)	24	1,271
Accumulated Loss	(27,508)	(69,376)
Accumulated Other Comprehensive Loss ("AOCI")	(27,484)	(68,105)
Cumulative Employer Contributions In Excess Of (or Below) Net Periodic Benefit Cost	(27,890)	12,138
Net Amount Recognized	(55,374)	(55,967)
Domestic plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Employee Contributions	0	0
Benefits Paid	(6,138)	(6,034)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	120,550	49,415
Actual Return on Plan Assets	10,759	10,663
Employer Contributions	2,302	1,087
Employee Contributions	0	0
Plan Settlements	(53,494)	0
Benefits Paid	(6,138)	(6,034)
Plan Expenses and Premiums Paid	(498)	(500)
Transfer In of Business Acquisition	0	65,919
Translation Difference	0	0
Fair Value of Plan Assets at End of Year	73,481	120,550	49,415
Domestic plan [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	153,723	58,734
Service Cost	491	434	383
Interest Cost	2,923	3,313	1,847
Employee Contributions	0	0
Effect of Plan Amendments	50	0
Plan Settlements	(53,494)	0
Defined Benefit Plan, Curtailments	0	0
Benefits Paid	(6,138)	(6,034)
Plan Expenses and Premiums Paid	0	0
Transfer In of Business Acquisition	0	86,414
Actuarial (gain) Loss	12,414	10,862
Translation Difference and Other	0	0
Benefit Obligation at End of Year	109,969	153,723	58,734
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	120,550
Employee Contributions	0	0
Benefits Paid	(6,138)	(6,034)
Fair Value of Plan Assets at End of Year	73,481	120,550
Defined Benefit Plan, Funded Status of Plan	(36,488)	(33,173)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current Asset	0	0
Current Liabilities	(612)	(2,620)
Non-current Liabilities	(35,876)	(30,553)
Net Amount Recognized	(36,488)	(33,173)
Amounts Not Yet Reflected in Net Periodic Benefit Costs and Included in Accumulated Other Comprehensive Income (Loss) [Abstract]
Prior Service credit (cost)	50	0
Accumulated Loss	(5,532)	(46,560)
Accumulated Other Comprehensive Loss ("AOCI")	(5,482)	(46,560)
Cumulative Employer Contributions In Excess Of (or Below) Net Periodic Benefit Cost	(31,006)	13,387
Net Amount Recognized	(36,488)	(33,173)
Domestic plan [Member] | Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	4,266	4,106
Service Cost	5	6	7
Interest Cost	77	143	130
Employee Contributions	0	0
Effect of Plan Amendments	0	0
Plan Settlements	0	0
Defined Benefit Plan, Curtailments		0
Benefits Paid	(250)	(384)
Plan Expenses and Premiums Paid	0	0
Transfer In of Business Acquisition	0	0
Actuarial (gain) Loss	(864)	395
Translation Difference and Other	0	0
Benefit Obligation at End of Year	3,234	4,266	4,106
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employee Contributions	0	0
Benefits Paid	(250)	(384)
Defined Benefit Plan, Funded Status of Plan	(3,234)	(4,266)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current Asset	0	0
Current Liabilities	(286)	(426)
Non-current Liabilities	(2,948)	(3,840)
Net Amount Recognized	(3,234)	(4,266)
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	124	(734)
Accumulated Other Comprehensive Loss ("AOCI")	124	(734)
Cumulative Employer Contributions In Excess Of (or Below) Net Periodic Benefit Cost	(3,358)	(3,532)
Net Amount Recognized	(3,234)	(4,266)
Foreign [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Employee Contributions	73	73
Benefits Paid	(5,087)	(3,832)
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	195,099	94,826
Actual Return on Plan Assets	20,367	13,458
Employer Contributions	6,912	5,223
Employee Contributions	73	73
Plan Settlements	(2,316)
Benefits Paid	(5,087)	(3,832)
Plan Expenses and Premiums Paid	(135)	(129)
Transfer In of Business Acquisition	0	81,068
Translation Difference	13,876	5,499
Fair Value of Plan Assets at End of Year	228,789	195,099	94,826
Foreign [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligation at Beginning of Year	217,893	111,316
Service Cost	4,340	3,507	3,426
Interest Cost	3,416	3,046	2,254
Employee Contributions	73	73
Effect of Plan Amendments	0	30
Plan Settlements	(2,316)	(1,087)
Defined Benefit Plan, Curtailments	(2,324)	0
Benefits Paid	(5,087)	(3,832)
Plan Expenses and Premiums Paid	(135)	(129)
Transfer In of Business Acquisition	0	85,658
Actuarial (gain) Loss	16,834	13,616
Translation Difference and Other	14,981	5,695
Benefit Obligation at End of Year	247,675	217,893	111,316
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets at Beginning of Year	195,099
Employee Contributions	73	73
Benefits Paid	(5,087)	(3,832)
Fair Value of Plan Assets at End of Year	18,074	195,099
Defined Benefit Plan, Funded Status of Plan	(18,886)	(22,794)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current Asset	6,748	0
Current Liabilities	(568)	(359)
Non-current Liabilities	(25,066)	(22,435)
Net Amount Recognized	(18,886)	(22,794)
Amounts Not Yet Reflected in Net Periodic Benefit Costs and Included in Accumulated Other Comprehensive Income (Loss) [Abstract]
Prior Service credit (cost)	(26)	1,271
Accumulated Loss	(21,976)	(22,816)
Accumulated Other Comprehensive Loss ("AOCI")	(22,002)	(21,545)
Cumulative Employer Contributions In Excess Of (or Below) Net Periodic Benefit Cost	3,116	(1,249)
Net Amount Recognized	(18,886)	(22,794)
Foreign [Member] | Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Employee Contributions	0	0
Defined Benefit Plan, Curtailments	0
Benefits Paid	(250)	(384)
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	250	384
Employee Contributions	0	0
Plan Settlements	0	0
Benefits Paid	(250)	(384)
Plan Expenses and Premiums Paid	0	0
Transfer In of Business Acquisition	0	0
Translation Difference	0	0
Fair Value of Plan Assets at End of Year	$ 0	$ 0	$ 0