Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities:
Net loss	$ (6,974)	$ (5,562)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of intangible assets	844	844
Depreciation and amortization of property and equipment	465	558
Gain on disposal of property and equipment	(27)	(5)
Stock-based compensation	1,389	1,285
Amortization of premium on marketable securities	0	1
Changes in operating assets and liabilities:
Accounts receivable, net	2,977	655
Inventories, net	(30)	403
Prepaid expenses and other current assets	5	(11)
Other assets	109	1
Accounts payable	(395)	(2,731)
Accrued compensation	974	654
Other accrued liabilities	1,172	(557)
Long term lease incentive	(106)	(106)
Deferred revenue	(184)	723
Net cash provided by (used in) operating activities	219	(3,848)
Investing activities:
Purchase of property and equipment	(265)	(52)
Proceeds from sale of property and equipment	27	5
Net cash used in investing activities	(238)	(47)
Financing activities:
Proceeds from exercises of options to purchase common stock	7	124
Taxes paid related to net share settlement of equity awards	(1,098)	(557)
Net cash used in financing activities	(1,091)	(433)
Net decrease in cash and cash equivalents	(1,110)	(4,328)
Cash and cash equivalents at the beginning of the period	23,273	26,487
Cash and cash equivalents at the end of the period	$ 22,163	$ 22,159