Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 14,348	$ 17,223
Short-term investments	41,160	55,002
Accounts receivable, net	10,465	12,436
Inventory	7,887	5,444
Prepaid expenses and other	5,402	5,242
Total current assets	79,262	95,347
Restricted cash	143	143
Property and equipment, net	6,875	6,366
Other assets	857	892
Total assets	87,137	102,748
Current liabilities:
Accounts payable	4,553	3,380
Accrued liabilities	6,598	10,403
Deferred revenue, current portion	4,001	4,627
Deferred rent, current portion	424	147
Long-term debt, current portion	271	251
Total current liabilities	15,847	18,808
Deferred revenue, net of current portion	7,098	7,135
Deferred rent, net of current portion	1,350	1,317
Long-term debt, net of current portion	30,903	30,675
Total liabilities	55,198	57,935
Commitment and contingencies
Stockholders' equity:
Preferred stock, $0.0001 par value, 15,000 shares authorized; none issued	0	0
Common stock, $0.0001 par value, 150,000 shares authorized; 18,392 and 18,272 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	2	2
Additional paid-in-capital	223,720	221,724
Accumulated other comprehensive loss	(19)	(43)
Accumulated deficit	(191,764)	(176,870)
Total stockholders' equity	31,939	44,813
Total liabilities and stockholders' equity	$ 87,137	$ 102,748