Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 31,219	$ 19,240
Accounts receivable, net of allowances of $34 at December 31, 2017 and $421 at December 31, 2016	11,800	5,924
Inventories	1,036	825
Prepaid expenses and other current assets	984	1,238
Total current assets	45,039	27,227
Restricted cash	1,557	1,624
Marketable securities	671	1,142
Property and equipment, net	2,815	2,155
Goodwill	3,241	3,241
Other non-current assets	302	259
Total assets	53,625	35,648
Current liabilities:
Accounts payable	3,545	4,232
Accrued compensation	4,753	4,314
Other accrued liabilities	4,362	2,111
Deferred revenue	12,292	1,710
Total current liabilities	24,952	12,367
Deferred revenue, net of current portion	1,501	1,066
Lease incentive obligation, net of current portion	460	885
Financing obligation, net of current portion	302	0
Other long-term liabilities	1,863	2,231
Total liabilities	29,078	16,549
Commitments and contingencies (Note 13)
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; 48,365 and 41,255 shares issued and outstanding at December 31, 2017 and December 31, 2016, respectively	5	4
Additional paid-in capital	340,079	311,164
Accumulated other comprehensive loss	(472)	0
Accumulated deficit	(315,065)	(292,069)
Total stockholders’ equity	24,547	19,099
Total liabilities and stockholders’ equity	$ 53,625	$ 35,648