Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net income	$ 13,301	$ 29,563	$ 19,674
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	8,732	8,016	6,573
Loss on disposal of property and equipment	33	1	17
Amortization and realized gain on available for sale securities	376	688	380
Deferred income tax assets	(403)	(56)	(84)
Credit loss on auction-rate securities			70
Tax benefit from stock option transactions	1,958	3,349	2,288
Excess tax benefit from stock option transactions	(27)	(1,256)	(643)
Stock-based compensation	13,126	16,810	14,611
Changes in operating assets and liabilities:
Accounts receivable	3,250	(2,826)	(6,406)
Inventories	5,699	(6,184)	(737)
Prepaid expenses and other current assets	673	378	(101)
Accounts payable	(957)	1,155	2,699
Accrued and other long-term liabilities	(438)	556	(5,633)
Accrued income taxes payable and noncurrent tax liabilities	(2,127)	(1,995)	(1,492)
Accrued compensation and related benefits	489	295	548
Net cash provided by operating activities	43,685	48,494	31,764
Cash flows from investing activities:
Property and equipment purchases	(21,022)	(22,779)	(9,954)
Purchase of intangible assets			(310)
Purchases of short-term investments	(78,250)	(208,621)	(159,917)
Proceeds from sale of short-term investments	129,719	197,243	80,586
Proceeds from sale of long-term investments	5,775	425	100
Changes in restricted assets		(19)	7,367
Net cash provided by (used in) investing activities	36,222	(33,751)	(82,128)
Cash flows from financing activities:
Proceeds from issuance of common stock	4,697	14,339	11,181
Proceeds from employee stock purchase plan	1,773	1,885	1,794
Repurchase of common stock	(38,472)	(31,527)
Excess tax benefits from stock option transactions	27	1,256	643
Net cash provided by (used in) financing activities	(31,975)	(14,047)	13,618
Effect of change in exchange rates	429	597	197
Net increase in cash and cash equivalents	48,361	1,293	(36,549)
Cash and cash equivalents, beginning of period	48,010	46,717	83,266
Cash and cash equivalents, end of period	96,371	48,010	46,717
Supplemental disclosures for cash flow information:
Cash paid for taxes	675	35	321
Supplemental disclosures of non-cash investing and financing activities:
Liability accrued for equipment purchases	1,483	4,264	663
Temporary impairment reversal of auction-rate securities	(270)	(160)	70
Other-than-temporary impairment of short-term investments			525
Value of auction-rate security put right			$ (525)