Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets, Current [Abstract]
Cash and cash equivalents	$ 286,217	$ 241,316
Accounts receivable, net	199,124	188,423
Contract assets, net	115,924	139,289
Inventories	118,129	110,478
Income taxes prepaid and receivable	3,509	5,940
Prepaid expenses and other current assets	29,021	31,830
Total current assets	751,924	717,276
Property, plant and equipment, net	426,806	448,554
Intangibles, net	41,020	46,869
Goodwill	183,568	187,553
Deferred income taxes	30,538	38,757
Noncurrent receivables, net	33,471	36,265
Other assets	72,916	74,662
Total assets	1,540,243	1,549,936
Liabilities, Current [Abstract]
Accounts payable	54,397	49,173
Accrued liabilities	112,481	125,459
Current maturities of long-term debt	0	9
Income taxes payable	14,623	16,222
Total current liabilities	181,501	190,863
Long-term debt	350,000	398,000
Other noncurrent liabilities	117,057	130,424
Deferred taxes and other liabilities	11,352	10,784
Total liabilities	659,910	730,071
SHAREHOLDERS' EQUITY
Preferred stock	0	0
Additional paid in capital	436,079	433,696
Retained earnings	841,162	770,746
Accumulated items of other comprehensive income:
Translation adjustments	(100,327)	(83,203)
Pension and postretirement liability adjustments	(39,059)	(39,661)
Derivative valuation adjustment	(5,525)	(9,544)
Treasury stock	(255,768)	(256,009)
Total Company shareholders' equity	876,603	816,066
Noncontrolling interest	3,730	3,799
Total equity	880,333	819,865
Total liabilities and shareholders' equity	1,540,243	1,549,936
Common Class A
SHAREHOLDERS' EQUITY
Common stock, par value	41	39
Common Class B
SHAREHOLDERS' EQUITY
Common stock, par value	$ 0	$ 2