Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 54,225	$ 31,219
Accounts receivable, net of allowances of $34 at September 30, 2018 and December 31, 2017	9,308	11,800
Inventories, net	830	1,036
Prepaid expenses and other current assets	2,219	984
Contract assets	1,868	0
Total current assets	68,450	45,039
Restricted cash	1,422	1,557
Marketable securities	652	671
Property and equipment, net	4,531	2,815
Goodwill	3,241	3,241
Other non-current assets	304	302
Total assets	78,600	53,625
Current liabilities:
Accounts payable	2,280	3,545
Accrued compensation	5,162	4,753
Other accrued liabilities	5,933	4,362
Deferred revenue	4,253	12,292
Total current liabilities	17,628	24,952
Deferred revenue, net of current portion	4,431	1,501
Lease incentive obligation, net of current portion	142	460
Financing obligation, net of current portion	122	302
Other long-term liabilities	1,504	1,863
Total liabilities	23,827	29,078
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; 53,935 shares and 48,365 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively	5	5
Additional paid-in capital	384,782	340,079
Accumulated other comprehensive loss	0	(472)
Accumulated deficit	(330,014)	(315,065)
Total stockholders' equity	54,773	24,547
Total liabilities and stockholders' equity	$ 78,600	$ 53,625