Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 85,066	$ 97,147	$ 80,296
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	58,208	55,623	54,305
Amortization	44,023	44,263	47,349
Share-based compensation expense	15,306	13,436	11,033
Provision for deferred income taxes	1,628	(16,284)	(13,313)
Charge for excess and obsolete inventory	9,405	9,302	8,311
Excess tax benefit from share-based compensation plans	0	0	(5,457)
Amortization of debt issuance costs	2,864	3,947	3,344
Loss on extinguishment of debt	20,687	0	0
Other	16,026	9,744	(20,299)
Changes in operating assets and liabilities, net of effects of acquisitions:
Trade accounts receivable and notes receivable	(15,401)	(25,298)	5,212
Inventories	(20,214)	(19,871)	(26,670)
Accounts payable and other accrued liabilities	15,975	31,294	(28,686)
Other current assets	(3,330)	185	654
Income taxes payable and refundable income taxes	64,516	3,408	4,955
Other	(1,386)	659	(116)
Net cash provided by operating activities	293,373	207,555	120,918
Investing activities:
Acquisition of property and equipment	(93,597)	(65,260)	(71,977)
Acquisition of business, net of cash acquired	(20,000)	0	0
Proceeds from sale or maturities of short-term investments	0	1,726	7,692
Other	1,142	(3,152)	647
Net cash used in investing activities	(112,455)	(66,686)	(63,638)
Financing activities:
Proceeds from long-term debt	550,000	0	0
Payments of long-term debt	(460,000)	(75,000)	(100,000)
Payments for debt issuance costs	(7,333)	0	0
Payments for debt extinguishment costs	(16,200)	0	0
Payments for dividends	(9,896)	0	0
Issuance of common stock from employee stock plans	5,566	4,844	4,264
Taxes paid related to net share settlement of equity awards	(5,887)	(4,018)	(2,508)
Repurchase and retirement of common stock	(28,000)	(7,573)	0
Other	(999)	0	5,457
Net cash provided by (used in) financing activities	27,251	(81,747)	(92,787)
Effect of exchange rate changes on cash and cash equivalents	10,850	(2,558)	(4,367)
Increase (decrease) in cash and cash equivalents	219,019	56,564	(39,874)
Cash and cash equivalents at beginning of year	406,389	349,825	389,699
Cash and cash equivalents at end of year	625,408	406,389	349,825
Supplemental Cash Flow Information
Equipment purchases in accounts payable	8,608	5,104	3,757
Capital lease obligations incurred	4,768	0	0
Schedule of interest and income taxes paid:
Interest paid	30,392	32,085	35,126
Income taxes, net of refunds received	$ 33,330	$ 35,722	$ 16,060