Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 28,973	$ 9,941
Short-term investments	56,837	32,715
Accounts receivable, net	7,429	8,331
Inventory	7,522	6,750
Prepaid expenses and other	3,567	2,999
Total current assets	104,328	60,736
Restricted cash	142	201
Deferred offering costs		29
Property and equipment, net	3,118	3,065
Other assets	205	341
Total assets	107,793	64,372
Current liabilities:
Accounts payable	2,619	3,354
Accrued liabilities	5,437	7,088
Deferred revenue, current portion	1,292	1,462
Deferred rent, current portion	605	590
Long-term debt, current portion	6,772	6,136
Total current liabilities	16,725	18,630
Deferred revenue, net of current portion	756	803
Deferred rent, net of current portion	1,168	1,313
Long-term debt, net of current portion	10,533	12,157
Total liabilities	29,182	32,903
Commitment and contingencies
Stockholders' equity:
Preferred stock, $0.0001 par value, 15,000 shares authorized; none issued
Common stock, $0.0001 par value, 150,000 shares authorized; 18,053 and 14,620 shares issued and outstanding, respectively	2	1
Additional paid-in-capital	216,854	158,278
Other comprehensive income	9	22
Accumulated deficit	(138,254)	(126,832)
Total stockholders' equity	78,611	31,469
Total liabilities and stockholders' equity	$ 107,793	$ 64,372