Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 17,223	$ 9,941
Short-term investments	55,002	32,715
Accounts receivable, net	12,436	8,331
Inventory	5,444	6,750
Prepaid expenses and other	5,242	2,999
Total current assets	95,347	60,736
Restricted cash	143	201
Deferred offering costs	0	29
Property and equipment, net	6,366	3,065
Other assets	892	341
Total assets	102,748	64,372
Current liabilities:
Accounts payable	3,380	3,354
Accrued liabilities	10,403	7,088
Deferred revenue, current portion	4,627	1,462
Deferred rent, current portion	147	590
Long-term debt, current portion	251	6,136
Total current liabilities	18,808	18,630
Deferred revenue, net of current portion	7,135	803
Deferred rent, net of current portion	1,317	1,313
Long-term debt, net of current portion	30,675	12,157
Total liabilities	57,935	32,903
Commitments and contingencies (Note 15)
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; 18,272 and 14,620 shares issued and outstanding at December 31, 2014 and 2013, respectively	2	1
Additional paid-in-capital	221,724	158,278
Other comprehensive income (loss)	(43)	22
Accumulated deficit	(176,870)	(126,832)
Total stockholders' equity	44,813	31,469
Total liabilities and stockholders' equity	$ 102,748	$ 64,372