CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 215,233	$ 187,385	$ 197,755	$ 154,744	$ 151,426	$ 183,727
Accounts receivable, net	220,584		223,176
Contract assets	54,431		57,447
Inventories	104,254		85,904
Income taxes prepaid and receivable	7,165		7,473
Prepaid expenses and other current assets	25,108		21,294
Total current assets	626,775		593,049
Property, plant and equipment, net	458,038		462,055
Intangibles, net	46,089		49,206
Goodwill	164,083		164,382
Deferred income taxes	66,082		62,622
Noncurrent receivables	45,651		45,061
Other assets	51,381		41,617
Total assets	1,458,099		1,417,992
LIABILITIES AND SHAREHOLDERS' EQUITY
Accounts payable	61,899		52,246
Accrued liabilities	120,693		129,030
Current maturities of long-term debt	19		1,224
Income taxes payable	14,078		6,806
Total current liabilities	196,689		189,306
Long-term debt	482,019		523,707
Other noncurrent liabilities	119,642		88,277
Deferred taxes and other liabilities	8,433		8,422
Total liabilities	806,783		809,712
SHAREHOLDERS' EQUITY
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid in capital	431,037		430,555
Retained earnings	641,297		589,645
Accumulated items of other comprehensive income:
Translation adjustments	(116,631)		(115,976)
Pension and postretirement liability adjustments	(48,636)		(47,109)
Derivative valuation adjustment	(2,849)		4,697
Treasury stock (Class A), at cost 8,408,770 shares in 2019 and 8,418,620 shares in 2018	(256,391)		(256,603)
Total Company shareholders' equity	647,868		605,249
Noncontrolling interest	3,448		3,031
Total equity	651,316	626,407	608,280	588,630	592,578	573,015
Total liabilities and shareholders' equity	1,458,099		1,417,992
Common Class A [Member]
SHAREHOLDERS' EQUITY
Common Stock	39		37
Accumulated items of other comprehensive income:
Total equity	39	37	37	37	37	37
Common Class B [Member]
SHAREHOLDERS' EQUITY
Common Stock	2		$ 3
Accumulated items of other comprehensive income:
Total equity	$ 2	$ 3		$ 3	$ 3	$ 3