CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Statement of Cash Flows [Abstract]
Noncontrolling Interest - purchase or sale	$ 477	$ (3,412)
Cash flows from operating activities:
Net income	96,939	43,664
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	92,324	91,519
Amortization	7,620	5,989
Deferred income tax expense	1,996	2,018
Dividends from unconsolidated entities	88	93
Other, net	2,485	2,567
Changes in assets and liabilities:
Accounts receivable	(29,022)	(26,633)
Inventories	(18,852)	(30,112)
Contract assets	(10,427)	0
Accounts payable	17,547	9,045
Accrued compensation	(10,438)	979
Advances on contracts	(12,339)	(6,534)
Retirement plan liabilities, net	(28,743)	(17,890)
Other assets and liabilities	(14,164)	8,200
Net cash provided by operating activities	95,014	82,905
Cash flows from investing activities:
Purchases of property, plant and equipment	(91,302)	(64,131)
Purchases of businesses, net of cash acquired	(56,389)	0
Proceeds from sales of assets	9,096	10,746
Net proceeds from settlement of foreign currency forward exchange contracts	3,244	4,450
Net cash used by investing activities	(135,351)	(48,935)
Cash flows from financing activities:
Short-term borrowings, net	(543)	1,915
Current maturities and long-term debt:
Additions	128,158	26,000
Reductions	(75,104)	(65,245)
Dividends paid to noncontrolling interests	(5,446)	(1,783)
Stock-based compensation - Employee taxes paid	(3,685)	(1,607)
Deferred financing costs	(537)	(42)
Other financing activities, net	0	(370)
Net cash provided (used) by financing activities	43,320	(44,544)
Effect of exchange rate changes on cash and cash equivalents, including restricted cash	(4,641)	4,058
Net decrease in cash and cash equivalents, including restricted cash	(1,658)	(6,516)
Cash and cash equivalents, including restricted cash, at beginning of period	66,209	71,879
Cash and cash equivalents, including restricted cash, at end of period	$ 64,551	$ 65,363