Consolidated Statements of Cash Flows (Unaudited) (USD $)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income	$ 7,989,000	$ 9,587,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,711,000	4,453,000
Loss on disposal of property and equipment		79,000
Amortization and realized gain on available-for-sale securities	204,000	87,000
Gain on auction-rate securities		(40,000)
Deferred income tax assets		(2,000)
Tax benefit from stock option transactions	4,877,000	1,929,000
Excess tax benefit from stock option transactions		(767,000)
Stock-based compensation	9,850,000	7,144,000
Changes in operating assets and liabilities:
Accounts receivable	(936,000)	(6,318,000)
Inventories	(8,140,000)	(9,350,000)
Prepaid expenses and other current assets	452,000	(297,000)
Accounts payable	4,057,000	5,912,000
Accrued liabilities	1,775,000	(999,000)
Accrued income taxes payable and noncurrent tax liabilities	(6,014,000)	(834,000)
Accrued compensation and related benefits	2,392,000	1,708,000
Net cash provided by operating activities	22,217,000	12,292,000
Cash flows from investing activities:
Property and equipment purchases	(10,801,000)	(13,184,000)
Proceeds from sale of property and equipment		13,000
Purchases of short-term investments	(40,385,000)	(86,774,000)
Proceeds from sale of short-term investments	37,800,000	61,518,000
Proceeds from sale of long-term investments	25,000	2,100,000
Net cash used in investing activities	(13,361,000)	(36,327,000)
Cash flows from financing activities:
Proceeds from issuance of common stock	16,184,000	7,341,000
Proceeds from employee stock purchase plan	1,167,000	1,036,000
Excess tax benefits from stock option transactions		767,000
Net cash provided by financing activities	17,351,000	9,144,000
Effect of change in exchange rates	424,000	164,000
Net increase (decrease) in cash and cash equivalents	26,631,000	(14,727,000)
Cash and cash equivalents, beginning of period	75,104,000	96,371,000
Cash and cash equivalents, end of period	101,735,000	81,644,000
Supplemental disclosures for cash flow information:
Cash paid for taxes	581,000	423,000
Supplemental disclosures of non-cash investing and financing activities:
Unpaid property and equipment purchases	3,744,000	4,414,000
Temporary impairment of auction-rate securities	$ 32,000	$ (99,000)