Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Operating activities:
Net loss	$ (10,862)	$ (13,402)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,676	2,119
Provision for doubtful accounts and other adjustments to accounts receivable	369	366
Provision for excess and obsolete inventory	34	54
Non-cash compensation related to stock options, ESPP and restricted stock	2,563	1,926
Change in operating accounts:
Accounts receivable	(195)	130
Income tax receivable	(3)	2
Inventories	(36)	(8)
Prepaid expenses and other assets	(550)	(375)
Accounts payable and accrued liabilities	(1,538)	568
Net cash used in operating activities	(8,542)	(8,620)
Investing activities:
Capital expenditures	(61)	(140)
Sales (purchases) of short-term investments	1,859	(973)
Net cash provided by (used in) investing activities	1,798	(1,113)
Financing activities:
Cash received from stock sale for employee stock purchase plan	11	21
Cash received from exercise of stock options	6
Net cash provided by financing activities	17	21
Net decrease in cash and cash equivalents	(6,727)	(9,712)
Cash and cash equivalents, beginning of period	11,763	18,873
Cash and cash equivalents, end of period	5,036	9,161
Supplemental disclosures of cash flow information:
Cash paid for income taxes	$ 42	$ 77