CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities:
Net income	$ 31,218	$ 13,259
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	10,325	10,926
Equity compensation expense	4,006	3,127
Deferred income taxes	1,570	(851)
Equity in undistributed income of unconsolidated joint ventures	(2,181)	(1,218)
Dividends received from unconsolidated joint ventures	1,754	1,785
Pension and other postretirement benefits	(79)	(50)
(Gain) loss on sale or disposal of property, plant and equipment	(89)	20
UTIS fire fixed asset and inventory write-offs	1,171	0
Provision (benefit) for credit losses	(345)	128
Changes in assets and liabilities:
Accounts receivable	(11,397)	(22,981)
Contract assets	(4,361)	2,276
Inventories	(6,894)	4,095
Pension and postretirement benefit contributions	(147)	(64)
Other current assets	(6,132)	(1,558)
Accounts payable and other accrued expenses	17,967	(733)
Other, net	135	472
Net cash provided by operating activities	36,521	8,633
Investing Activities:
Capital expenditures	(3,602)	(11,160)
Net cash used in investing activities	(3,602)	(11,160)
Financing Activities:
Proceeds from borrowings under revolving credit facility	0	150,000
Repayment of debt principal and finance lease obligations	(21,253)	(96)
Payments of taxes related to net share settlement of equity awards	(2,632)	(4,997)
Proceeds from issuance of shares to employee stock purchase plan	704	664
Net cash (used in) provided by financing activities	(23,181)	145,571
Effect of exchange rate fluctuations on cash	(2,414)	(1,616)
Net increase in cash and cash equivalents	7,324	141,428
Cash and cash equivalents at beginning of period	191,785	166,849
Cash and cash equivalents at end of period	199,109	308,277
Supplemental Disclosures:
Accrued capital additions	2,814	2,525
Interest, net of amounts capitalized	607	1,386
Income taxes	$ 9,337	$ 13,218