Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010
Cash Flows from Operating Activities:
Net income	$ 123,756	$ 104,940
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	35,388	34,117
Loss on disposal of property and equipment	481	1,500
(Decrease) increase in deferred compensation liability	(320)	135
Provision for uncollectible accounts	997	1,506
Provision for deferred income taxes	598	1,379
Share-based compensation expense	11,497	9,787
Tax benefit from exercises of stock options and vesting of restricted stock units	(14,009)	(13,293)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	(16,181)	(6,916)
Inventories	(9,732)	(22,460)
Other assets	3,056	(5,836)
Accounts payable	8,305	6,107
Accrued liabilities	16,664	16,447
Deferred revenue	3,018	2,570
Net cash provided by operating activities	163,518	129,983
Cash Flows from Investing Activities:
Purchases of property and equipment	(39,927)	(28,646)
Proceeds from sale of property and equipment	223	86
Proceeds from disposition of pharmaceutical product lines	3,000
Acquisition of intangible assets		(244)
Acquisition of a business, net of cash acquired	(2,600)
Net cash used by investing activities	(39,304)	(28,804)
Cash Flows from Financing Activities:
Borrowings on revolving credit facilities, net	24,903	7,135
Payment of notes payable	(643)	(605)
Repurchases of common stock	(166,016)	(117,157)
Proceeds from exercises of stock options and employee stock purchase plans	26,080	22,055
Tax benefit from exercises of stock options and vesting of restricted stock units	14,009	13,293
Net cash used by financing activities	(101,667)	(75,279)
Net effect of changes in exchange rates on cash	2,037	884
Net increase in cash and cash equivalents	24,584	26,784
Cash and cash equivalents at beginning of period	156,915	106,728
Cash and cash equivalents at end of period	$ 181,499	$ 133,512

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Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits are not generally reported as cash and cash equivalents. Includes cash and cash equivalents associated with the entity's continuing operations. Excludes cash and cash equivalents associated with the disposal group (and discontinued operation).