CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets, Current [Abstract]
Cash and cash equivalents	$ 215,304	$ 195,540
Accounts receivable, net	210,326	218,271
Contract assets, net	104,853	79,070
Inventories	113,107	95,149
Income taxes prepaid and receivable	6,560	6,162
Prepaid expenses and other current assets	30,485	24,142
Total current assets	680,635	618,334
Property, plant and equipment, net	442,469	466,462
Intangibles, net	48,281	52,892
Goodwill	184,287	180,934
Deferred income taxes	38,387	51,621
Noncurrent receivables, net	36,228	41,234
Other assets	60,405	62,891
Total assets	1,490,692	1,474,368
Liabilities, Current [Abstract]
Accounts payable	46,740	65,203
Accrued liabilities	119,221	125,885
Current maturities of long-term debt	12	20
Income taxes payable	12,936	11,611
Total current liabilities	178,909	202,719
Long-term debt	418,000	424,009
Other noncurrent liabilities	134,903	132,725
Deferred taxes and other liabilities	9,022	12,226
Total liabilities	740,834	771,679
SHAREHOLDERS' EQUITY
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued	0	0
Additional paid in capital	432,823	432,518
Retained earnings	749,678	698,496
Accumulated items of other comprehensive income:
Translation adjustments	(119,814)	(122,852)
Pension and postretirement liability adjustments	(49,436)	(49,994)
Derivative valuation adjustment	(10,409)	(3,135)
Treasury stock (Class A), at cost; 8,394,022 shares in 2020 and 8,408,770 shares in 2019	(256,074)	(256,391)
Total Company shareholders' equity	746,809	698,683
Noncontrolling interest	3,049	4,006
Total equity	749,858	702,689
Total liabilities and shareholders' equity	1,490,692	1,474,368
Common Class A [Member]
SHAREHOLDERS' EQUITY
Common stock	39	39
Common Class B [Member]
SHAREHOLDERS' EQUITY
Common stock	$ 2	$ 2