Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Operating activities
Net income	$ 22,460	$ 23,277
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	11,448	11,345
Amortization of premiums on investments, net of accretion of discounts	2,037	2,673
Stock-based compensation	6,152	6,036
Excess tax benefit from employee stock-based compensation	(1,246)	(1,425)
Deferred revenue	477	97
Deferred income tax	(245)	(615)
Loss on disposal of property and equipment	52	24
Changes in assets and liabilities
Trade and other accounts receivable	(8,117)	(2,816)
Inventories	(3,506)	3,420
Prepaid expenses	(4,062)	(2,116)
Other current assets	1,161	(536)
Other long-term assets	199	(132)
Accounts payable	2,228	(3,196)
Accrued salaries and employee benefits	(7,725)	(7,847)
Other accrued expenses	4,566	(40)
Income tax payable	5,902	11,500
Other long-term liabilities	(49)	456
Net cash provided by operating activities	31,732	40,105
Investing activities
Proceeds from sales and maturities of marketable securities	144,227	30,460
Purchases of marketable securities	(127,119)	(5,731)
Purchases of property, plant and equipment	(9,265)	(10,762)
Purchases of capitalized software	(1,738)	(780)
Purchases of intangible assets, including licenses and manufacturing access fees	(825)	(923)
Other	408	501
Net cash provided by investing activities	5,688	12,765
Financing activities
Repurchase and retirement of common stock	0	(47,972)
Proceeds from issuance of common stock and employee stock purchase plan shares	14,232	17,390
Repurchase and retirement of restricted stock for payment of taxes	(1,124)	(358)
Excess tax benefit from employee stock-based compensation	1,246	1,425
Borrowings	0	10,000
Net cash provided by (used in) financing activities	14,354	(19,515)
Effect of exchange rate changes on cash and cash equivalents	(21)	518
Net increase in cash and cash equivalents	51,753	33,873
Cash and cash equivalents at the beginning of period	87,021	59,690
Cash and cash equivalents at the end of period	$ 138,774	$ 93,563