Condensed Consolidated Statements Of Cash Flows (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash Flows from Operating Activities:
Net income	$ 46,593,000	$ 44,867,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	13,394,000	13,513,000
(Gain) loss on disposal of property and equipment	(18,000)	27,000
(Decrease) increase in deferred compensation liability	(86,000)	114,000
Provision for uncollectible accounts	451,000	644,000
(Benefit of) provision for deferred income taxes	(835,000)	1,169,000
Share-based compensation expense	4,108,000	3,949,000
Tax benefit from share-based compensation arrangements	(6,747,000)	(5,310,000)
Changes in assets and liabilities:
Accounts receivable	(21,707,000)	(23,722,000)
Inventories	2,200,000	(10,717,000)
Other assets	1,312,000	6,301,000
Accounts payable	1,857,000	5,567,000
Accrued liabilities	(10,231,000)	(16,216,000)
Deferred revenue	3,227,000	869,000
Net cash provided by operating activities	33,518,000	21,055,000
Cash Flows from Investing Activities:
Purchases of property and equipment	(11,298,000)	(20,132,000)
Proceeds from disposition of pharmaceutical product lines		3,500,000
Acquisitions of intangible assets	(175,000)	(659,000)
Acquisition of businesses, net of cash acquired	(1,161,000)
Net cash used by investing activities	(12,634,000)	(17,291,000)
Cash Flows from Financing Activities:
Borrowings on revolving credit facilities, net	38,000,000	48,000,000
Debt issue costs	(139,000)
Payment of notes payable	(253,000)	(238,000)
Repurchases of common stock	(70,279,000)	(63,778,000)
Proceeds from exercises of stock options and employee stock purchase plans	10,964,000	12,958,000
Tax benefit from share-based compensation arrangements	6,747,000	5,310,000
Net cash (used) provided by financing activities	(14,960,000)	2,252,000
Net effect of changes in exchange rates on cash	1,221,000	(1,638,000)
Net increase in cash and cash equivalents	7,145,000	4,378,000
Cash and cash equivalents at beginning of period	279,058,000	279,058,000
Cash and cash equivalents at end of period	286,203,000	228,364,000
Supplemental Disclosure of Non-Cash Information:
Market value of common shares received from employees in connection with share-based compensation - see Note 18	$ 5,000,000	$ 4,100,000