Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash Flows From Operating Activities
Net income	$ 63,639	$ 59,808
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	40,500	37,729
Deferred compensation	749	5,392
Realized and unrealized gains on long-term investments	(504)	(2,576)
Stock-based compensation	3,387	4,551
Deferred income taxes	2,463	2,741
Other non-cash items	830	2,972
Changes in assets and liabilities:
Receivables, net	(23,969)	(33,697)
Inventories	(14,409)	(1,477)
Other current assets	442	(2,050)
Accounts payable and accrued liabilities	(18,579)	(11,777)
Pension liabilities	(122)	(58)
Environmental and legal liabilities	(479)	(469)
Deferred revenues	(162)	(162)
Net Cash Provided By Operating Activities	53,786	60,927
Cash Flows From Investing Activities
Expenditures for property, plant and equipment	(43,741)	(38,331)
Business acquisition (Note 16)	(21,475)	(4,339)
Other, net	1,775	(2,184)
Net Cash Used In Investing Activities	(63,441)	(44,854)
Cash Flows From Financing Activities
Revolving debt and bank overdrafts, net	1,893	(7,221)
Other debt repayments	(5,714)	(5,714)
Dividends paid	(10,160)	(9,225)
Company stock repurchased	(12,000)	(1,500)
Stock option exercises	3,274	2,518
Other, net	(4,432)	(1,586)
Net Cash Used In Financing Activities	(27,139)	(22,728)
Effect of Exchange Rate Changes on Cash	(5,364)	4,730
Net Decrease in Cash and Cash Equivalents	(42,158)	(1,925)
Cash and Cash Equivalents at Beginning of Period	298,894	225,743
Cash and Cash Equivalents at End of Period	256,736	223,818
Supplemental Cash Flow Information
Cash payments of income taxes, net of refunds/payments	19,739	18,288
Cash payments of interest	$ 6,444	$ 7,101