Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Cash Flows From Operating Activities
Net income	[1]	$ 103,101	$ 111,105	[2],[3]	$ 100,743	[3]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		78,701	81,115		79,022
Deferred compensation		15,140	(2,329)		4,857
Realized and unrealized gain on long-term investments		(3,955)	2,966		(4,178)
Stock-based compensation		8,872	6,837		7,151
Deferred income taxes	[1]	(5,016)	10,355		(1,001)
Other non-cash items		2,240	4,622		4,857
Changes in assets and liabilities, excluding effects of acquisitions:
Receivables, net		4,894	5,196		(16,358)
Inventories	[1]	28,460	(24,678)		(1,990)
Other current assets		(680)	832		(489)
Accounts payable and accrued liabilities		(15,084)	(19,023)		30,476
Pension liabilities		(790)	(5,065)		(1,960)
Environmental and legal liabilities		2,519	(478)		(1,142)
Deferred revenues		26	(324)		(1,125)
Net Cash Provided By Operating Activities		218,428	171,131		198,863
Cash Flows From Investing Activities
Expenditures for property, plant and equipment		(105,572)	(86,647)		(78,613)
Business acquisitions, net of cash acquired (Note 21)		(9,000)	(22,852)		(4,339)
Other, net		1,905	1,684		269
Net Cash Used In Investing Activities		(112,667)	(107,815)		(82,683)
Cash Flows From Financing Activities
Revolving debt and bank overdrafts, net		(7,495)	6,045		(6,008)
Other debt repayments		(46,429)	(20,714)		(20,714)
Dividends paid		(23,097)	(20,857)		(18,907)
Company stock repurchased		(13,184)	(15,500)		(6,000)
Stock option exercises		3,037	4,163		3,370
Other, net		(3,326)	(4,785)		(2,238)
Net Cash Used In Financing Activities		(90,494)	(51,648)		(50,497)
Effect of Exchange Rate Changes on Cash		(78)	(10,368)		7,468
Net Increase in Cash and Cash Equivalents		15,189	1,300		73,151
Cash and Cash Equivalents at Beginning of Year		300,194	298,894		225,743
Cash and Cash Equivalents at End of Year		315,383	300,194		298,894
Supplemental Cash Flow Information
Cash payments of income taxes, net of refunds		29,331	32,973		25,661
Cash payments of interest		$ 12,250	$ 12,829		$ 13,889

[1] The 2018 and 2017 amounts for the noted line items have been retrospectively changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from LIFO to FIFO.

[2] The 2018 amounts for the noted line items have been retrospectively changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from LIFO to FIFO

[3] The retained earnings and net income amounts for the noted line items have been retrospectively changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from LIFO to FIFO.