CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 40,445	$ 41,826
Short-term investments	85,159	87,201
Accounts receivable, net	33,027	35,193
Inventories, net	22,826	19,896
Prepaid and other current assets	4,571	3,769
Total current assets	186,028	187,885
Property and equipment, net	17,182	17,151
Operating lease right-of-use assets	10,087
Other long-term assets	353	128
Total assets	214,698	206,294
Current liabilities:
Accounts payable	11,206	6,824
Accrued expense	3,376	3,930
Employee-related liabilities	17,047	24,030
Deferred revenue	5,460	4,600
Common stock warrants	29,762	17,926
Operating lease liabilities	3,703
Other current liabilities	6,126	8,978
Total current liabilities	76,680	66,288
Deferred rent—long-term		3,799
Operating lease liabilities - long-term	10,685
Other long-term liabilities	6,371	4,932
Total liabilities	93,736	75,019
Commitments and contingencies (Note 9)
Stockholders’ equity:
Common stock, $0.001 par value; 200,000 shares authorized as of March 31, 2019 and December 31, 2018. 57,982 and 57,554 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively.	58	57
Additional paid-in capital	743,930	731,306
Accumulated other comprehensive income (loss)	41	(13)
Accumulated deficit	(623,067)	(600,075)
Total stockholders’ equity	120,962	131,275
Total liabilities and stockholders’ equity	214,698	206,294
Patents [Member]
Current assets:
Patents, net	$ 1,048	$ 1,130