Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows from Operating Activities:
Net income	$ 192,135	$ 181,951	$ 187,794
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	68,956	58,888	54,596
Amortization on marketable securities, net	1,432
Impairment charge	8,212
Provision for uncollectible accounts	2,200	2,035	1,601
Provision for deferred income taxes	5,143	830	2,073
Share-based compensation expense	19,884	18,099	16,539
Other	(472)	(160)	614
Tax benefit from share-based compensation arrangements	(11,315)	(16,078)	(14,158)
Changes in assets and liabilities:
Accounts receivable	(50,142)	(3,626)	(15,946)
Inventories	(34,969)	(38,310)	(1,347)
Accounts payable	(2,468)	6,703	(4,399)
Deferred revenue	(319)	14,195	6,442
Other assets and liabilities	18,087	11,319	12,187
Net cash provided by operating activities	216,364	235,846	245,996
Cash Flows from Investing Activities:
Purchases of property and equipment	(82,921)	(60,523)	(77,612)
Purchase of marketable securities	(271,958)
Proceeds from the sale and maturities of marketable securities	56,775
Proceeds from disposition of pharmaceutical product lines			3,500
Proceeds from sale of equity investment		5,400
Acquisitions of intangible assets		(175)	(1,024)
Acquisitions of a businesses, net of cash acquired	(10,302)	(25,115)	(10,923)
Net cash used by investing activities	(308,406)	(80,413)	(86,059)
Cash Flows from Financing Activities:
Borrowings on revolving credit facilities, net	24,000	272,000	65,000
Issuance of senior notes	250,097	200,000	150,000
Debt issue costs	(1,380)	(1,406)	(976)
Payment of notes payable		(1,394)	(1,107)
Repurchases of common stock	(401,981)	(618,158)	(367,761)
Proceeds from exercises of stock options and employee stock purchase plans	22,397	29,442	38,235
Tax benefit from share-based compensation arrangements	11,315	16,078	14,158
Net cash used by financing activities	(95,552)	(103,438)	(102,451)
Net effect of changes in exchange rates on cash	(5,948)	(8,517)	(2,414)
Net increase (decrease) in cash and cash equivalents	(193,542)	43,478	55,072
Cash and cash equivalents at beginning of period	322,536	279,058	223,986
Cash and cash equivalents at end of period	128,994	322,536	279,058
Supplemental Disclosures of Cash Flow Information:
Interest paid	27,187	12,284	5,024
Income taxes paid	$ 54,877	$ 60,239	$ 67,721