Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows From Operating Activities
Net income	$ 30,716	$ 31,912
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	19,948	18,707
Deferred compensation	1,614	376
Realized and unrealized gains on long-term investments	(97)	(1,645)
Stock-based compensation	2,232	1,385
Deferred income taxes	357	2,543
Other non-cash items	31	721
Changes in assets and liabilities:
Receivables, net	(24,225)	(20,263)
Inventories	(8,993)	(14,396)
Other current assets	(684)	(1,694)
Accounts payable and accrued liabilities	(19,518)	(14,184)
Pension liabilities	(116)	(127)
Environmental and legal liabilities	(225)	24
Deferred revenues	(81)	(81)
Net Cash Provided By Operating Activities	959	3,278
Cash Flows From Investing Activities
Expenditures for property, plant and equipment	(27,358)	(20,396)
Business acquisition (Note 16)	(21,475)	(4,339)
Other, net	1,781	(1,887)
Net Cash Used In Investing Activities	(47,052)	(26,622)
Cash Flows From Financing Activities
Revolving debt and bank overdrafts, net	79
Other debt repayments		(441)
Dividends paid	(5,092)	(4,606)
Company stock repurchased	(2,500)	(1,500)
Stock option exercises	3,155	835
Other, net	(4,395)	(1,486)
Net Cash Used In Financing Activities	(8,753)	(7,198)
Effect of Exchange Rate Changes on Cash	533	2,608
Net Decrease in Cash and Cash Equivalents	(54,313)	(27,934)
Cash and Cash Equivalents at Beginning of Period	298,894	225,743
Cash and Cash Equivalents at End of Period	244,581	197,809
Supplemental Cash Flow Information
Cash payments of income taxes, net of refunds/payments	3,345	5,603
Cash payments of interest	$ 2,071	$ 2,164