Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash Flows from Operating Activities:
Net income	$ 144,557	$ 134,927
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	41,130	38,490
Loss on disposal of property and equipment	220	194
Increase in deferred compensation liability	226	176
Provision for uncollectible accounts	1,226	837
Provision for deferred income taxes	(984)	(1,861)
Share-based compensation expense	12,265	11,684
Tax benefit from share-based compensation arrangements	(7,438)	(10,182)
Changes in assets and liabilities:
Accounts receivable	(12,795)	255
Inventories	(6,360)	(18,078)
Other assets	4,717	539
Accounts payable	2,184	(4,893)
Accrued liabilities	(3,269)	(3,751)
Deferred revenue	4,050	5,151
Net cash provided by operating activities	179,729	153,488
Cash Flows from Investing Activities:
Purchases of property and equipment	(60,607)	(43,230)
Proceeds from disposition of pharmaceutical product lines	3,500	3,000
Proceeds from sale of property and equipment		45
Acquisitions of intangible assets	(1,024)	(900)
Acquisition of a business, net of cash acquired	(10,101)
Net cash used by investing activities	(68,232)	(41,085)
Cash Flows from Financing Activities:
Borrowings (payments) on revolving credit facilities, net	185,200	(11,000)
Payment of notes payable	(858)	(682)
Repurchases of common stock	(282,910)	(91,152)
Proceeds from exercises of stock options and employee stock purchase plans	21,734	17,156
Tax benefit from share-based compensation arrangements	7,438	10,182
Net cash used by financing activities	(69,396)	(75,496)
Net effect of changes in exchange rates on cash	(1,276)	639
Net increase in cash and cash equivalents	40,825	37,546
Cash and cash equivalents at beginning of period	223,986	183,895
Cash and cash equivalents at end of period	$ 264,811	$ 221,441