CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating Activities:
Net income	$ 43,465	$ 47,928
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	22,084	21,536
Equity compensation expense	5,814	5,327
Deferred income taxes	3,879	4,813
Equity in undistributed income of unconsolidated joint ventures	(2,811)	(1,976)
Dividends received from unconsolidated joint ventures	1,809	616
Pension and postretirement benefits	(796)	(794)
Realized (gain) loss from sale of property, plant and equipment	383	942
Bad debt expense	(190)	61
Proceeds from insurance related to operations	0	826
Changes in operating assets and liabilities, excluding effects of acquisitions:
Accounts receivable	(9,446)	(13,220)
Contract assets	(21,933)	0
Inventories	(6,489)	(6,464)
Pension and postretirement benefit contributions	(338)	(147)
Other current assets	(1,299)	(1,991)
Accounts payable and other accrued expenses	(13,835)	7,213
Other, net	3,287	1,703
Net cash provided by operating activities	22,818	64,489
Investing Activities:
Acquisition of business, net of cash received	0	(60,191)
Capital expenditures	(20,177)	(9,696)
Proceeds from insurance claims	0	922
Proceeds from the sale of property, plant and equipment, net	1,027	1,641
Net cash used in investing activities	(19,150)	(67,324)
Financing Activities:
Line of credit issuance costs	0	(1,169)
Repayment of debt principal and capital lease obligations	(291)	(50,178)
Repurchases of capital stock	(2,999)	0
Proceeds from the exercise of stock options, net	698	1,905
Payments of taxes related to net share settlement of equity awards	(6,427)	(2,617)
Proceeds from issuance of shares to employee stock purchase plan	558	422
Net cash used in financing activities	(8,461)	(51,637)
Effect of exchange rate fluctuations on cash	(1,666)	4,017
Net decrease in cash and cash equivalents	(6,459)	(50,455)
Cash and cash equivalents at beginning of period	181,159	227,767
Cash and cash equivalents at end of period	174,700	177,312
Supplemental Disclosures:
Interest, net of amounts capitalized	2,631	3,085
Income taxes	$ 14,040	$ 13,913