CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 151,426	$ 183,727	$ 143,333	$ 181,742
Accounts receivable, net	248,538	202,675
Contract assets	42,895
Inventories	100,034	136,519
Income taxes prepaid and receivable	6,132	6,266
Prepaid expenses and other current assets	18,675	14,520
Total current assets	567,700	543,707
Property, plant and equipment, net	459,388	454,302
Intangibles, net	53,881	55,441
Goodwill	168,311	166,796
Deferred income taxes	70,174	68,648
Noncurrent receivables	35,338	32,811
Other assets	45,543	39,493
Total assets	1,400,335	1,361,198
LIABILITIES AND SHAREHOLDERS' EQUITY
Notes and loans payable	226	262
Accounts payable	45,694	44,899
Accrued liabilities	122,103	105,914
Current maturities of long-term debt	1,821	1,799
Income taxes payable	5,182	8,643
Total current liabilities	175,026	161,517
Long-term debt	518,656	514,120
Other noncurrent liabilities	100,170	101,555
Deferred taxes and other liabilities	11,339	10,991
Total liabilities	805,191	788,183
SHAREHOLDERS' EQUITY
Preferred stock, par value $5.00 per share; authorized 2,000,000 shares; none issued
Additional paid in capital	428,859	428,423
Retained earnings	533,759	534,082
Accumulated items of other comprehensive income:
Translation adjustments	(69,672)	(87,318)
Pension and postretirement liability adjustments	(50,549)	(50,536)
Derivative valuation adjustment	6,433	1,953
Treasury stock (Class A), at cost 8,431,335 shares in 2018 and 2017	(256,876)	(256,876)
Total Company shareholders' equity	591,994	569,768
Noncontrolling interest	3,150	3,247
Total equity	595,144	573,015
Total liabilities and shareholders' equity	1,400,335	1,361,198
Common Class A [Member]
SHAREHOLDERS' EQUITY
Common Stock	37	37
Common Class B [Member]
SHAREHOLDERS' EQUITY
Common Stock	$ 3	$ 3