Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating activities
Net loss	$ (20,454)	$ (11,847)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,360	1,467
Amortization of debt discount	162	113
Stock-based compensation	766	566
Revaluation of preferred stock warrant liability	(1,156)	(150)
Net amortization of premium on short-term investments	89
Interest accrued on long-term notes	182	63
Loss on disposal of property and equipment	1	1
Changes in operating assets and liabilities
Accounts receivable	(3,470)	(999)
Inventory	(336)	(409)
Prepaid expenses and other	(1,500)	(1,443)
Other assets	(275)	(7)
Accounts payable	1,121	628
Accrued liabilities	2,038	1,379
Deferred revenue	556	31
Deferred rent	(567)	(533)
Net cash used in operating activities	(21,483)	(11,140)
Investing activities
Purchases of property and equipment	(500)	(312)
Purchase of short-term investments	(33,006)
Net cash used in investing activities	(33,506)	(312)
Financing activities
Net proceeds from initial public offering	47,374
Proceeds from issuance of long-term debt	5,000	7,500
Repayment of long-term debt	(163)	(1,654)
Proceeds from exercise of stock options	378	99
Net cash provided by financing activities	52,589	5,945
Net decrease in cash and cash equivalents	(2,400)	(5,507)
Cash and cash equivalents
Beginning of period	21,692	10,868
End of period	$ 19,292	$ 5,361