Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 22,352	$ 23,273
Accounts receivable, net of allowances of $421 at June 30, 2016 and December 31, 2015	3,340	7,329
Inventories	1,155	992
Prepaid expenses and other current assets	1,055	1,245
Total current assets	27,902	32,839
Restricted cash	787	787
Marketable securities	1,115	1,549
Property and equipment, net	2,403	3,109
Intangible assets, net	1,125	2,812
Goodwill	3,241	3,241
Other non-current assets	283	310
Total assets	36,856	44,647
Current liabilities:
Accounts payable	2,651	3,399
Accrued compensation	2,844	3,331
Other accrued liabilities	2,829	2,013
Deferred revenue	4,118	6,098
Total current liabilities	12,442	14,841
Deferred revenue, net of current portion	1,354	3,120
Lease incentive obligation, net of current portion	1,098	1,310
Other long-term liabilities	2,282	2,497
Liabilities	17,176	21,768
Commitments and contingencies (Note 10)
Stockholders' equity:
Preferred stock, $0.0001 par value per share; 5,000 shares authorized; none issued and outstanding	0	0
Common stock, $0.0001 par value per share; 100,000 shares authorized; 41,171 shares and 40,343 shares issued and outstanding at June 30, 2016 and December 31, 2015, respectively	4	4
Additional paid-in capital	307,951	305,981
Accumulated other comprehensive income (loss)	(29)	405
Accumulated deficit	(288,246)	(283,511)
Total stockholders' equity	19,680	22,879
Total liabilities and stockholders' equity	$ 36,856	$ 44,647