Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net loss	$ (3,644)	$ (3,610)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Stock-based compensation	961	625
Depreciation and amortization	327	331
Other	106	97
Changes in assets and liabilities:
Accounts receivable	737	3,091
Inventories	(867)	(634)
Other current assets and prepaid expenses	(15)	(792)
Other long-term assets	(1)	303
Accounts payable	(228)	663
Accrued liabilities	(2,781)	(1,534)
Other long-term liabilities	(72)	(70)
Deferred revenue	(559)	548
Income tax liability	22	10
Net cash used in operating activities	(6,014)	(972)
Cash flows from investing activities:
Acquisition of property, equipment and software	(407)	(239)
Proceeds from sales of marketable investments	5,376	3,200
Proceeds from maturities of marketable investments	12,180	7,240
Purchase of marketable investments	(8,867)	(16,791)
Net cash provided by (used in) investing activities	8,282	(6,590)
Cash flows from financing activities:
Repurchase of common stock	(4,550)
Proceeds from exercise of stock options and employee stock purchase plan	6,002	2,096
Payments on capital lease obligations	(61)	(33)
Net cash provided by financing activities	1,391	2,063
Net increase (decrease) in cash and cash equivalents	3,659	(5,499)
Cash and cash equivalents at beginning of period	9,803	16,242
Cash and cash equivalents at end of period	13,462	10,743
Supplemental disclosure of non-cash items:
Repurchase of common stock acquired but not settled	$ 656