Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 33,394	$ 27,780
Restricted cash	509	2,664
Short-term investments	65,446	70,020
Accounts receivable, net of allowance for doubtful accounts of $384 and $103 at September 30, 2018 and December 31, 2017, respectively	7,666	12,465
Contract assets	3,237	6,278
Inventories	6,275	5,514
Income Tax Receivable	205	0
Prepaid expenses and other current assets	2,329	1,342
Total current assets	119,061	126,063
Restricted cash, non-current	86	182
Contract assets, non-current	108	0
Long-term investments	2,341	0
Deferred tax assets, non-current	18,082	7,933
Property and equipment, net	15,634	13,393
Operating lease, right of use asset	12,428	2,843
Goodwill	12,790	12,790
Other intangible assets, net	796	1,269
Other assets, non-current	287	12
Total assets	181,613	164,485
Current liabilities:
Accounts payable	4,515	4,091
Accrued expenses and other current liabilities	6,646	7,948
Lease liabilities	764	1,603
Income taxes payable	0	432
Accrued warranty reserve	409	366
Contract liabilities	15,899	15,909
Current portion of long-term debt	12	11
Total current liabilities	28,245	30,360
Long-term debt, less current portion	7	16
Lease liabilities, non-current	12,797	1,698
Contract liabilities, non-current	30,727	40,517
Other non-current liabilities	242	0
Total liabilities	72,018	72,591
Commitments and Contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued or outstanding at September 30, 2018 and December 31, 2017	0	0
Common stock, $0.001 par value; 200,000,000 shares authorized; 59,230,828 shares issued and 53,774,893 shares outstanding at September 30, 2018 and 58,168,433 shares issued and 53,905,600 shares outstanding at December 31, 2017	59	58
Additional paid-in capital	157,008	149,006
Accumulated comprehensive loss	(101)	(125)
Treasury stock, at cost, 5,455,935 shares repurchased at September 30, 2018 and 4,262,833 shares repurchased at December 31, 2017	(30,486)	(20,486)
Accumulated deficit	(16,885)	(36,559)
Total stockholders’ equity	109,595	91,894
Total liabilities and stockholders’ equity	$ 181,613	$ 164,485