Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES
Net income	$ 118,768	$ 97,243	$ 133,383
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	65,130	63,328	62,085
Amortization	9,125	9,377	8,710
Change in deferred taxes and other liabilities	12,181	11,101	13,702
Impairment of property, plant and equipment	856	1,173	3,119
Non-cash interest expense	875	(290)	605
Write-off of pension liability adjustments due to settlement/curtailment	0	411	450
Compensation and benefits paid or payable in Class A Common Stock	3,146	1,505	2,063
Provision for credit losses from uncollected receivables and contract assets	(1,299)	1,628	309
Foreign currency remeasurement (gain)/loss on intercompany loans	(3,150)	14,246	(3,730)
Fair value adjustment on foreign currency options	169	0	0
Changes in operating assets and liabilities that provided/(used) cash:
Accounts receivable	(7,734)	31,522	9,278
Contract assets	25,446	(59,122)	(19,199)
Inventories	(9,942)	(13,685)	(8,923)
Prepaid expenses and other current assets	(998)	(7,811)	(2,291)
Income taxes prepaid and receivable	3,944	113	1,390
Accounts payable	9,492	(15,586)	10,524
Accrued liabilities	(774)	(3,856)	(7,393)
Income taxes payable	(477)	5,939	3,979
Noncurrent receivables	4,355	4,158	(1,341)
Other noncurrent liabilities	(13,713)	(2,437)	(6,573)
Other, net	2,075	1,296	205
Net cash provided by operating activities	217,475	140,253	200,352
INVESTING ACTIVITIES
Purchase of business, net of cash acquired	0	0	(30,793)
Purchases of property, plant and equipment	(52,793)	(41,463)	(67,358)
Purchased software	(906)	(927)	(597)
Net cash used in investing activities	(53,699)	(42,390)	(98,748)
FINANCING ACTIVITIES
Proceeds from borrowings	8,000	75,000	45,000
Principal payments on debt	(56,009)	(101,020)	(120,017)
Principal payments on finance lease liabilities	(1,438)	(7,214)	(1,180)
Debt acquisition costs	0	(2,432)	0
Purchase of Treasury shares	(23,449)	0	0
Taxes paid in lieu of share issuance	(998)	(490)	(971)
Proceeds from options exercised	153	55	112
Dividends paid	(25,894)	(24,568)	(23,251)
Net cash used in financing activities	(99,635)	(60,669)	(100,307)
Effect of exchange rate changes on cash and cash equivalents	(3,421)	8,582	(3,512)
Increase/(decrease) in cash and cash equivalents	60,720	45,776	(2,215)
Cash and cash equivalents at beginning of period	241,316	195,540	197,755
Cash and cash equivalents at end of period	$ 302,036	$ 241,316	$ 195,540