Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 53,039	$ 31,219
Accounts receivable, net of allowances of $34 at December 31, 2018 and 2017	11,551	11,447
Unbilled receivables, current	1,916	353
Inventories	589	1,036
Prepaid expenses and other current assets	1,068	984
Contract assets	35	0
Total current assets	68,198	45,039
Restricted cash	1,446	1,557
Equity securities	588	671
Property and equipment, net	4,759	2,815
Goodwill	3,241	3,241
Other non-current assets	1,051	302
Total assets	79,283	53,625
Current liabilities:
Accounts payable	3,050	3,545
Accrued compensation	5,272	4,753
Other accrued liabilities	4,855	4,362
Deferred revenue	4,936	12,292
Total current liabilities	18,113	24,952
Deferred revenue, net of current portion	3,352	1,501
Lease incentive obligation, net of current portion	35	460
Capital lease obligation, net of current portion	61	302
Other long-term liabilities	1,416	1,863
Total liabilities	22,977	29,078
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; 54,065 and 48,365 shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively	5	5
Additional paid-in capital	386,775	340,079
Accumulated other comprehensive loss	0	(472)
Accumulated deficit	(330,474)	(315,065)
Total stockholders’ equity	56,306	24,547
Total liabilities and stockholders’ equity	$ 79,283	$ 53,625