CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities:
Net income	$ 194,766	$ 220,029	$ 205,604
Adjustments to reconcile net income to net cash provided by operations:
Depreciation	156,292	142,755	145,485
Amortization	15,455	10,339	9,317
Stock based compensation	19,561	18,924	19,824
Provision for (recovery of) doubtful accounts	923	235	561
(Gain) loss on disposition of fixed assets	(770)	387	(348)
Gain on remeasurement of equity securities	(6,500)		(2,013)
Debt prepayment costs		4,710
Deferred income taxes	(23,352)	2,238	(11,112)
Defined benefit plan expense	19,501	17,200	16,786
Equity in results of affiliates	229	229	191
Changes in balance sheet items, excluding effects from acquisitions and foreign currency adjustments:
Accounts receivables	(66,968)	(44,658)	(41,721)
Inventories	(25,183)	(12,989)	(834)
Prepaid and other current assets	(9,437)	(33,959)	(5,968)
Accounts payable and accrued liabilities	37,155	58,245	(12,474)
Income taxes payable	(3,155)	(8,753)	15,056
Retirement and deferred compensation plan liabilities	(22,762)	(41,004)	(9,380)
Other changes, net	27,873	(9,199)	(3,675)
Net Cash Provided by Operations	313,628	324,729	325,299
Cash Flows from Investing Activities:
Capital expenditures	(211,252)	(156,624)	(128,986)
Proceeds from sale of property and equipment	4,466	2,036	1,693
Insurance proceeds	10,631	709	986
Settlement for derivative		(66,155)
Maturity of short-term investments			29,485
Acquisition of business, net of cash acquired	(527,916)		(202,985)
Acquisition of intangible assets	(611)		(2,492)
Proceeds from sale of investment in unconsolidated affiliate			1,204
Investment in equity securities	(10,000)	(5,000)
Notes receivable, net	(779)	234	593
Net Cash Used by Investing Activities	(735,461)	(224,800)	(300,502)
Cash Flows from Financing Activities:
Proceeds from notes payable	49,069
Repayments of notes payable	(29,994)
Proceeds and repayments of short term credit facility, net	81,063	(169,213)	163,148
Proceeds from long-term obligations	13,161	625,628	5,963
Repayments of long-term obligations	(72,290)	(165,798)	(55,314)
Dividends paid	(82,346)	(79,944)	(76,659)
Credit facility costs		(3,542)
Debt prepayment costs		(4,710)
Proceeds from stock option exercises	88,156	73,905	55,347
Purchase of treasury stock	(3,905)	(120,540)
Common stock repurchased and retired	(57,786)	(40,994)	(131,371)
Excess tax benefit from exercise of stock options			9,171
Net Cash Provided (Used) by Financing Activities	(14,872)	114,792	(29,715)
Effect of Exchange Rate Changes on Cash	(9,112)	31,632	(18,696)
Net Increase (Decrease) in Cash and Equivalents and Restricted Cash	(445,817)	246,353	(23,614)
Cash and Equivalents and Restricted Cash at Beginning of Period	712,640	466,287	489,901
Cash and Equivalents and Restricted Cash at End of Period	266,823	712,640	466,287
Supplemental Cash Flow Disclosure:
Interest paid	32,005	38,838	36,265
Income taxes paid	$ 96,048	$ 77,349	$ 82,201