CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating Activities:
Net income	$ 59,873	$ 27,779
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	20,997	25,858
Equity compensation expense	8,394	7,022
Deferred income taxes	3,881	(8,976)
Equity in undistributed income of unconsolidated joint ventures	(4,111)	(2,240)
Dividends received from unconsolidated joint ventures	1,754	1,785
Pension settlement benefits	0	(63)
Pension and other postretirement benefits	(190)	(100)
(Gain) loss on sale or disposal of property, plant and equipment	(682)	53
UTIS fire fixed asset and inventory write-offs	1,211	0
Provision (benefit) for credit losses	(342)	54
Changes in assets and liabilities:
Accounts receivable	(24,609)	(6,623)
Proceeds from insurance/government subsidies related to operations	148	0
Contract assets	(3,710)	3,174
Inventories	(10,527)	7,910
Pension and postretirement benefit contributions	(151)	(244)
Other current assets	(3,767)	414
Accounts payable and other accrued expenses	14,547	(6,129)
Other, net	3,490	5,285
Net cash provided by operating activities	66,206	54,959
Investing Activities:
Capital expenditures	(21,415)	(18,150)
Proceeds from the sale of property, plant and equipment, net	714	0
Net cash used in investing activities	(20,701)	(18,150)
Financing Activities:
Proceeds from borrowings under revolving credit facility	0	150,000
Repayment of debt principal and finance lease obligations	(29,652)	(50,193)
Payments of taxes related to net share settlement of equity awards	(2,684)	(5,029)
Proceeds from issuance of shares to employee stock purchase plan	704	664
Net cash (used in) provided by financing activities	(31,632)	95,442
Effect of exchange rate fluctuations on cash	(1,713)	(358)
Net increase in cash and cash equivalents	12,160	131,893
Cash and cash equivalents at beginning of period	191,785	166,849
Cash and cash equivalents at end of period	203,945	298,742
Supplemental Disclosures:
Accrued capital additions	7,403	4,144
Interest, net of amounts capitalized	964	3,311
Income taxes	$ 18,036	$ 15,644