Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 93,421	$ 53,039
Accounts receivable, net of allowances of $34 at June 30, 2019 and December 31, 2018	11,814	11,551
Unbilled receivables, current	2,336	1,916
Inventories	720	589
Prepaid expenses and other current assets	1,950	1,068
Contract assets	0	35
Total current assets	110,241	68,198
Restricted cash	1,749	1,446
Equity securities	419	588
Right-of-use assets - Operating leases, net	25,240	0
Right-of-use assets - Finance leases, net	384	0
Property and equipment, net	5,312	4,759
Goodwill	3,241	3,241
Other non-current assets	207	1,051
Total assets	146,793	79,283
Current liabilities:
Accounts payable	2,164	3,050
Accrued compensation	4,551	5,272
Other accrued liabilities	4,059	4,855
Current portion of lease obligations - Operating leases	683	0
Current portion of lease obligations - Finance leases	183	0
Deferred revenue	5,851	4,936
Total current liabilities	17,491	18,113
Deferred revenue, net of current portion	3,249	3,352
Long-term lease obligations - Operating leases	26,147	0
Long-term lease obligations - Finance leases	0	61
Lease incentive obligation, net of current portion	0	35
Other long-term liabilities	1,222	1,416
Total liabilities	48,109	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; 57,940 shares and 54,065 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	6	5
Additional paid-in capital	440,795	386,775
Accumulated deficit	(342,117)	(330,474)
Total stockholders' equity	98,684	56,306
Total liabilities and stockholders' equity	$ 146,793	$ 79,283