CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Assets, Current [Abstract]
Cash and cash equivalents	$ 204,037	$ 195,540
Accounts receivable, net	202,612	218,271
Contract assets, net	96,092	79,070
Inventories	115,532	95,149
Income taxes prepaid and receivable	5,998	6,162
Prepaid expenses and other current assets	26,209	24,142
Total current assets	650,480	618,334
Property, plant and equipment, net	443,046	466,462
Intangibles, net	49,706	52,892
Goodwill	181,302	180,934
Deferred income taxes	40,999	51,621
Noncurrent receivables, net	36,901	41,234
Other assets	59,526	62,891
Total assets	1,461,960	1,474,368
Liabilities, Current [Abstract]
Accounts payable	50,181	65,203
Accrued liabilities	115,458	125,885
Current maturities of long-term debt	17	20
Income taxes payable	11,546	11,611
Total current liabilities	177,202	202,719
Long-term debt	435,000	424,009
Other noncurrent liabilities	134,898	132,725
Deferred taxes and other liabilities	8,702	12,226
Total liabilities	755,802	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	432,738	432,518
Retained earnings	726,233	698,496
Accumulated items of other comprehensive income:
Translation adjustments	(139,635)	(122,852)
Pension and postretirement liability adjustments	(48,962)	(49,994)
Derivative valuation adjustment	(11,030)	(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	703,311	698,683
Noncontrolling interest	2,847	4,006
Total equity	706,158	702,689
Total liabilities and shareholders' equity	1,461,960	1,474,368
Common Class A [Member]
SHAREHOLDERS' EQUITY
Common stock	39	39
Common Class B [Member]
SHAREHOLDERS' EQUITY
Common stock	$ 2	$ 2