Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income	$ 133,383	$ 83,019	$ 32,585
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	62,085	68,800	61,517
Amortization	8,710	10,236	10,439
Change in deferred taxes and other liabilities	13,702	8,972	(1,264)
Provision for write-off of property, plant and equipment	3,119	3,707	2,870
Non-cash interest expense	605	459	660
Write-off of pension liability adjustment due to settlement/curtailment	450	1,494
Compensation and benefits paid or payable in Class A Common Stock	2,063	2,203	2,133
Write-off of intangible assets in a discontinued product line			4,149
Changes in operating assets and liabilities that provided/(used) cash, net of impact of business acquisition:
Accounts receivable	9,587	(19,139)	(21,859)
Contract assets	(19,199)	(10,267)
Inventories	(8,923)	(968)	3,090
Prepaid expenses and other current assets	(2,291)	(5,815)	(4,989)
Income taxes prepaid and receivable	1,390	(1,402)	(941)
Accounts payable	10,524	9,340	2,910
Accrued liabilities	(7,393)	8,209	5,303
Income taxes payable	3,979	(824)	(799)
Noncurrent receivable	(1,341)	(12,249)	(18,766)
Noncurrent liabilities	(6,573)	(5,479)	(10,145)
Other, net	(3,525)	(7,811)	(2,677)
Net cash provided by operating activities	200,352	132,485	64,216
Investing Activities
Purchase of business, net of cash acquired	(30,793)
Purchases of property, plant and equipment	(67,358)	(81,579)	(85,510)
Purchased software	(597)	(1,307)	(2,127)
Net cash used in investing activities	(98,748)	(82,886)	(87,637)
Financing Activities
Proceeds from borrowings	45,000	26,031	115,334
Principal payments on debt	(120,017)	(29,913)	(84,047)
Principal payments on finance lease liabilities	(1,180)
Debt acquisition costs			(2,130)
Cash received to settle swap agreements			6,346
Taxes paid in lieu of share issuance	(971)	(1,652)	(1,364)
Proceeds from options exercised	112	202	597
Dividends paid	(23,251)	(21,926)	(21,869)
Net cash (used in)/provided by financing activities	(100,307)	(27,258)	12,867
Effect of exchange rate changes on cash and cash equivalents	(3,512)	(8,313)	12,539
Increase/(decrease) in cash and cash equivalents	(2,215)	14,028	1,985
Cash and cash equivalents at beginning of year	197,755	183,727	181,742
Cash and cash equivalents at end of year	$ 195,540	$ 197,755	$ 183,727