CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities:
Net income	$ 47,319	$ 87,651	$ 80,459
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation and amortization	49,162	50,073	44,099
Equity compensation expense	12,305	11,223	11,818
Deferred income taxes	(17,549)	(3,325)	17,513
Equity in undistributed income of unconsolidated joint ventures	(5,319)	(5,501)	(4,898)
Dividends received from unconsolidated joint ventures	5,375	4,431	3,529
Pension settlement charges	53,213	0	0
Pension and other postretirement benefits	(943)	(1,552)	(1,561)
Asbestos-related charges	1,720	704	3,400
Loss (gain) on sale or disposal of property, plant and equipment	756	(164)	(5,154)
Impairment charges	1,537	1,506	807
Provision (benefit) for doubtful accounts	437	236	(439)
Changes in assets and liabilities:
Accounts receivable	20,677	(3,824)	(14,059)
Contract assets	273	(22,728)	0
Inventories	(1,200)	(19,013)	(14,208)
Pension and postretirement benefit contributions	(103)	(25,354)	(906)
Other current assets	(1,519)	(648)	(576)
Accounts payable and other accrued expenses	(9,139)	(7,886)	12,341
Proceeds from insurance related to operations	0	0	932
Other, net	4,321	991	5,885
Net cash provided by operating activities	161,323	66,820	138,982
Investing Activities:
Acquisition of business, net of cash received	0	(77,969)	(60,191)
Isola asset acquisition	0	(43,434)	0
Capital expenditures	(51,597)	(47,115)	(27,215)
Proceeds from the sale of property, plant and equipment, net	9	1,081	8,095
Proceeds from insurance claims	0	0	1,041
Return of capital from unconsolidated joint ventures	2,625	0	0
Net cash used in investing activities	(48,963)	(167,437)	(78,270)
Financing Activities:
Proceeds from borrowings under revolving credit facility	0	102,500	0
Line of credit issuance costs	0	0	(1,169)
Repayment of debt principal and finance lease obligations	(105,886)	(6,162)	(110,689)
Payments of taxes related to net share settlement of equity awards	(7,550)	(6,600)	(5,309)
Proceeds from the exercise of stock options, net	344	861	3,085
Proceeds from issuance of shares to employee stock purchase plan	1,249	1,082	895
Share repurchases	0	(2,999)	0
Net cash (used in) provided by financing activities	(111,843)	88,682	(113,187)
Effect of exchange rate fluctuations on cash	(1,406)	(1,486)	5,867
Net decrease in cash and cash equivalents	(889)	(13,421)	(46,608)
Cash and cash equivalents at beginning of period	167,738	181,159	227,767
Cash and cash equivalents at end of period	166,849	167,738	181,159
Supplemental Disclosures:
Accrued capital additions	3,420	2,744	2,376
Interest, net of amounts capitalized	7,762	7,040	5,787
Income taxes	$ 17,593	$ 29,161	$ 36,918