Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 2,499,000	$ 2,995,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,709,000	2,184,000
Loss on disposal of property and equipment		74,000
Amortization and realized gain on available-for-sale securities	98,000	28,000
Deferred income tax assets		(2,000)
Tax benefit from stock option transactions	2,914,000	649,000
Excess tax benefit from stock option transactions	(132,000)	(100,000)
Stock-based compensation	4,660,000	3,315,000
Changes in operating assets and liabilities:
Accounts receivable	(3,285,000)	(4,849,000)
Inventories	(2,836,000)	(1,443,000)
Prepaid expenses and other current assets	315,000	97,000
Accounts payable	2,135,000	4,098,000
Accrued liabilities	1,889,000	2,207,000
Accrued income taxes payable and noncurrent tax liabilities	(3,440,000)	(432,000)
Accrued compensation and related benefits	(822,000)	(2,602,000)
Net cash provided by operating activities	6,704,000	6,219,000
Cash flows from investing activities:
Property and equipment purchases	(3,435,000)	(4,875,000)
Purchases of short-term investments	(17,590,000)	(49,415,000)
Proceeds from sale of short-term investments	21,250,000	25,000,000
Proceeds from sale of long-term investments	25,000	100,000
Net cash provided by (used in) investing activities	250,000	(29,190,000)
Cash flows from financing activities:
Proceeds from issuance of common stock	9,839,000	3,985,000
Proceeds from employee stock purchase plan	1,167,000	1,036,000
Excess tax benefits from stock option transactions	132,000	100,000
Net cash provided by financing activities	11,138,000	5,121,000
Effect of change in exchange rates	91,000	210,000
Net increase (decrease) in cash and cash equivalents	18,183,000	(17,640,000)
Cash and cash equivalents, beginning of period	75,104,000	96,371,000
Cash and cash equivalents, end of period	93,287,000	78,731,000
Supplemental disclosures for cash flow information:
Cash paid for taxes	324,000	125,000
Supplemental disclosures of non-cash investing and financing activities:
Liability accrued for property and equipment purchases	4,230,000	3,099,000
Temporary impairment of auction-rate securities	$ 15,000	$ (90,000)