CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Activities:
Net income	$ 13,259	$ 28,399
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	10,926	12,984
Equity compensation expense	3,127	2,476
Deferred income taxes	(851)	(2,505)
Equity in undistributed income of unconsolidated joint ventures	(1,218)	(837)
Dividends received from unconsolidated joint ventures	1,785	1,741
Pension and other postretirement benefits	(50)	(174)
Loss on sale or disposal of property, plant and equipment	20	273
Provision (benefit) for doubtful accounts	128	(158)
Changes in assets and liabilities:
Accounts receivable	(22,981)	(16,948)
Contract assets	2,276	(4,588)
Inventories	4,095	(1,550)
Pension and postretirement benefit contributions	(64)	(6)
Other current assets	(1,558)	(2,605)
Accounts payable and other accrued expenses	(733)	(327)
Other, net	472	885
Net cash provided by operating activities	8,633	17,060
Investing Activities:
Capital expenditures	(11,160)	(12,647)
Proceeds from the sale of property, plant and equipment, net	0	7
Return of capital from unconsolidated joint ventures	0	2,625
Net cash used in investing activities	(11,160)	(10,015)
Financing Activities:
Proceeds from borrowings under revolving credit facility	150,000	0
Repayment of debt principal and finance lease obligations	(96)	(5,098)
Payments of taxes related to net share settlement of equity awards	(4,997)	(7,140)
Proceeds from the exercise of stock options, net	0	285
Proceeds from issuance of shares to employee stock purchase plan	664	587
Net cash provided by (used in) financing activities	145,571	(11,366)
Effect of exchange rate fluctuations on cash	(1,616)	(1,343)
Net increase (decrease) in cash and cash equivalents	141,428	(5,664)
Cash and cash equivalents at beginning of period	166,849	167,738
Cash and cash equivalents at end of period	308,277	162,074
Supplemental Disclosures:
Accrued capital additions	2,525	2,068
Interest, net of amounts capitalized	1,386	2,161
Income taxes	$ 13,218	$ 2,014