Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Operating activities
Net loss	$ (37,658)	$ (20,454)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,115	1,360
Stock-based compensation	3,604	766
Net amortization of premium on short-term investments	127	89
Amortization of debt discount	51	162
Revaluation of preferred stock warrant liability	0	(1,156)
Loss on extinguishment of debt	581	0
Interest accrued on long-term notes	(348)	182
Accrued interest converted to principal balance of term loan	179	0
Loss on disposal of property and equipment	0	1
Gain on sale of investments	(5)	0
Changes in operating assets and liabilities
Accounts receivable	(6,935)	(3,470)
Inventory	(1,198)	(336)
Prepaid expenses and other	(1,218)	(1,500)
Other assets	120	(275)
Accounts payable	(1,210)	1,121
Accrued liabilities	667	2,038
Deferred revenue	9,328	556
Deferred rent	(382)	(567)
Net cash used in operating activities	(33,182)	(21,483)
Investing activities
Purchases of property and equipment	(1,284)	(500)
Decrease in restricted cash	59	0
Proceeds from sale of short-term investments	4,500	0
Proceeds from maturity of short-term investments	26,675	0
Purchase of short-term investments	(47,271)	(33,006)
Net cash used in investing activities	(17,321)	(33,506)
Financing activities
Borrowings under long-term debt agreements	20,000	5,000
Deferred costs related to long-term debt agreement	(770)	0
Repayment of long-term debt	(18,151)	(163)
Net proceeds from public offering	57,015	47,374
Proceeds from exercise of common stock warrants	230	0
Repurchase of shares related to common stock warrant exercise	(94)	0
Proceeds from employee stock purchase plan	988	0
Proceeds from exercise of stock options	170	378
Net cash provided by financing activities	59,388	52,589
Net increase (decrease) in cash and cash equivalents	8,885	(2,400)
Cash and cash equivalents
Beginning of period	9,941	21,692
End of period	$ 18,826	$ 19,292