Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 15,399,000	$ 15,508,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	8,960,000	6,866,000
Loss on disposal of property and equipment		79,000
Amortization and loss on investments	320,000	145,000
Gain on auction-rate securities		(40,000)
Excess tax benefit from stock option transactions		(835,000)
Stock-based compensation	15,081,000	11,326,000
Changes in operating assets and liabilities:
Accounts receivable	(2,573,000)	(6,464,000)
Inventories	(10,851,000)	(12,519,000)
Prepaid expenses and other current assets	463,000	(490,000)
Accounts payable	1,164,000	2,345,000
Accrued liabilities	3,492,000	(345,000)
Accrued income taxes payable and noncurrent tax liabilities	(215,000)	1,254,000
Accrued compensation and related benefits	(1,002,000)	(3,380,000)
Net cash provided by operating activities	30,238,000	13,450,000
Cash flows from investing activities:
Property and equipment purchases	(15,424,000)	(18,735,000)
Proceeds from sale of property and equipment		13,000
Purchases of intangible assets		(459,000)
Premiums paid on deferred compensation plan	(309,000)
Purchases of short-term investments	(62,374,000)	(115,709,000)
Proceeds from sale of short-term investments	55,700,000	86,168,000
Proceeds from sale of long-term investments	25,000	2,100,000
Net cash used in investing activities	(22,382,000)	(46,622,000)
Cash flows from financing activities:
Proceeds from issuance of common stock	32,654,000	12,233,000
Proceeds from employee stock purchase plan	2,145,000	1,852,000
Repurchases of common stock	(7,973,000)
Excess tax benefits from stock option transactions		835,000
Net cash provided by financing activities	26,826,000	14,920,000
Effect of change in exchange rates	660,000	128,000
Net increase (decrease) in cash and cash equivalents	35,342,000	(18,124,000)
Cash and cash equivalents, beginning of period	75,104,000	96,371,000
Cash and cash equivalents, end of period	110,446,000	78,247,000
Supplemental disclosures for cash flow information:
Cash paid for taxes	847,000	732,000
Supplemental disclosures of non-cash investing and financing activities:
Liability accrued for property and equipment purchases	2,081,000	1,687,000
Temporary impairment of auction-rate securities	$ (117,000)	$ (141,000)