CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows from Operating Activities:
Net income	$ 220,029	$ 205,604	$ 199,295
Adjustments to reconcile net income to net cash provided by operations:
Depreciation	142,755	145,485	134,647
Amortization	10,339	9,317	4,246
Stock based compensation	18,924	19,824	20,612
Provision for (recovery of) doubtful accounts	235	561	(813)
Gain on sale of investment in unconsolidated affiliate		(2,013)
Debt prepayment costs	4,710
Deferred income taxes	2,238	(11,112)	(7,141)
Defined benefit plan expense	17,200	16,786	20,685
Equity in results of affiliates	229	191	718
Changes in balance sheet items, excluding effects from foreign currency adjustments:
Accounts receivables	(44,658)	(41,721)	(27,759)
Inventories	(12,989)	(834)	(18,925)
Prepaid and other current assets	(33,959)	(5,968)	(6,982)
Accounts payable and accrued liabilities	58,245	(12,474)	39,330
Income taxes payable	(8,753)	15,056	3,397
Retirement and deferred compensation plan liabilities	(41,004)	(9,380)	(30,332)
Other changes, net	(8,812)	(4,023)	(7,219)
Net Cash Provided by Operations	324,729	325,299	323,759
Cash Flows from Investing Activities:
Capital expenditures	(156,624)	(128,986)	(149,323)
Proceeds from sale of property and equipment	2,036	1,693	827
Insurance proceeds	709	986	3,739
Settlement for derivative	(66,155)
Purchase of short-term investments			(32,769)
Maturity of short-term investments		29,485
Acquisition of business, net of cash acquired		(202,985)
Acquisition of intangible assets		(2,492)
Proceeds from sale of investment in unconsolidated affiliate		1,204
Investment in unconsolidated affiliate	(5,000)
Notes receivable, net	234	593	1,296
Net Cash Used by Investing Activities	(224,800)	(300,502)	(176,230)
Cash Flows from Financing Activities:
Proceeds from (repayments of) notes payable	(169,213)	163,148	(227,362)
Proceeds from long-term obligations	625,628	5,963	225,236
Repayments of long-term obligations	(165,798)	(55,314)	(16,981)
Dividends paid	(79,944)	(76,659)	(71,247)
Credit facility costs	(3,542)		(1,216)
Debt prepayment costs	(4,710)
Proceeds from stock option exercises	73,905	55,347	64,759
Purchase of treasury stock	(120,540)
Common stock repurchased and retired	(40,994)	(131,371)	(13,887)
Excess tax benefit from exercise of stock options		9,171	8,388
Net Cash Provided (Used) by Financing Activities	114,792	(29,715)	(32,310)
Effect of Exchange Rate Changes on Cash	31,632	(18,696)	(25,080)
Net Increase (Decrease) in Cash and Equivalents	246,353	(23,614)	90,139
Cash and Equivalents at Beginning of Period	466,287	489,901	399,762
Cash and Equivalents at End of Period	712,640	466,287	489,901
Supplemental Cash Flow Disclosure:
Interest paid	38,838	36,265	31,664
Income taxes paid	$ 77,349	$ 82,201	$ 79,502