Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net income	$ 2,995	$ 1,893
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,184	2,270
Loss on disposal of property and equipment	74
Amortization and realized gain on debt instruments	28	183
Deferred income tax assets	(2)
Tax benefit from stock option transactions	649	1,472
Excess tax benefit from stock option transactions	(100)	(435)
Stock-based compensation	3,315	2,987
Changes in operating assets and liabilities:
Accounts receivable	(4,849)	705
Inventories	(1,443)	2,679
Prepaid expenses and other current assets	97	(345)
Accounts payable	4,098	1,299
Accrued and other long-term liabilities	2,207	(347)
Accrued income taxes payable and noncurrent tax liabilities	(432)	(1,037)
Accrued compensation and related benefits	(2,602)	(3,094)
Net cash provided by operating activities	6,219	8,230
Cash flows from investing activities:
Property and equipment purchases	(4,875)	(3,056)
Purchases of short-term investments	(49,415)	(15,968)
Proceeds from sale of short-term investments	25,000	43,530
Proceeds from sale of long-term investments	100	2,050
Net cash provided by (used in) investing activities	(29,190)	26,556
Cash flows from financing activities:
Proceeds from issuance of common stock	3,985	3,527
Proceeds from employee stock purchase plan	1,036	928
Repurchase of common stock		(13,710)
Excess tax benefits from stock option transactions	100	435
Net cash provided by (used in) financing activities	5,121	(8,820)
Effect of change in exchange rates	210	86
Net increase (decrease) in cash and cash equivalents	(17,640)	26,052
Cash and cash equivalents, beginning of period	96,371	48,010
Cash and cash equivalents, end of period	78,731	74,062
Supplemental disclosures for cash flow information:
Cash paid for taxes	125	100
Supplemental disclosures of non-cash investing and financing activities:
Liability accrued for equipment purchases	3,099	3,464
Temporary impairment reversal of auction-rate securities	$ (90)	$ (140)