Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 47,322	$ 53,039
Accounts receivable, net of allowances of $34 at March 31, 2019 and December 31, 2018	12,604	11,551
Unbilled receivables, current	1,923	1,916
Inventories	633	589
Prepaid expenses and other current assets	1,232	1,068
Contract assets	0	35
Total current assets	63,714	68,198
Restricted cash	1,785	1,446
Equity securities	484	588
Right-of-use assets - Operating leases, net	25,913	0
Right-of-use assets - Finance leases, net	438	0
Property and equipment, net	4,535	4,759
Goodwill	3,241	3,241
Other non-current assets	1,013	1,051
Total assets	101,123	79,283
Current liabilities:
Accounts payable	2,180	3,050
Accrued compensation	6,469	5,272
Other accrued liabilities	7,127	4,855
Current portion of lease obligations - Operating leases	1,091	0
Current portion of lease obligations - Finance leases	233	0
Deferred revenue	1,554	4,936
Total current liabilities	18,654	18,113
Deferred revenue, net of current portion	3,797	3,352
Long-term lease obligations - Operating leases	26,133	0
Long-term lease obligations - Finance leases	9	61
Lease incentive obligation, net of current portion	0	35
Other long-term liabilities	1,320	1,416
Total liabilities	49,913	22,977
Commitments and Contingencies (Note 11)
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; 54,541 shares and 54,065 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	5	5
Additional paid-in capital	386,815	386,775
Accumulated deficit	(335,610)	(330,474)
Total stockholders' equity	51,210	56,306
Total liabilities and stockholders' equity	$ 101,123	$ 79,283