Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities:
Net loss	$ (29,281)	$ (17,708)	$ (10,932)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	1,777	1,947	1,454
Amortization of debt discount	213	136	330
Stock-based compensation	1,145	745	243
Revaluation of preferred stock warrant liability	(1,156)	387	(73)
Amortization of premium on short-term investments	(518)
Interest accrued on convertible promissory notes			87
Interest accrued on long-term note loan	259	90
Loss on disposal of property and equipment	1	3
Changes in operating assets and liabilities
Accounts receivable	(5,009)	(210)	(965)
Inventory	(1,370)	(1,884)	(1,338)
Prepaid expenses and other	(1,679)	221	(1,100)
Related party loans and other assets	(268)	118	(58)
Accounts payable	1,601	103	(1,231)
Accrued liabilities	2,678	1,830	781
Deferred revenue	1,025	146	624
Deferred rent	(764)	(732)	1,486
Net cash used in operating activities	(31,346)	(14,808)	(10,692)
Investing activities:
Purchases of property and equipment	(759)	(428)	(2,688)
Purchases of short-term investments	(32,175)
Increase in restricted cash	(21)		(112)
Net cash used in investing activities	(32,955)	(428)	(2,800)
Financing activities:
Proceeds from issuance of preferred stock and warrants		15,132	14,883
Proceeds from initial public offering	47,374
Proceeds from issuance of convertible promissory notes and warrants			5,000
Proceeds from issuance of long-term debt	5,000	13,000	5,004
Repayment of long-term debt	(211)	(1,706)	(4,899)
Deferred offering costs		(553)
Proceeds from exercise of stock options and warrants	387	187	6
Net cash provided by financing activities	52,550	26,060	19,994
Net increase (decrease) in cash and cash equivalents	(11,751)	10,824	6,502
Cash and cash equivalents:
Beginning of year	21,692	10,868	4,366
End of year	9,941	21,692	10,868
Supplemental disclosures:
Accretion of preferred stock	4,653	7,533	5,251
Accrual of offering costs	29	1,212
Cash paid for interest	1,474	563	167
Issuance of preferred stock warrants with debt	138	648	661
Issuance of preferred stock warrants with equity			1,867
Conversion of convertible promissory notes and accrued interest into Series D preferred stock			5,087
Conversion of convertible preferred stock to common stock	108,275
Conversion of convertible preferred stock warrants to common stock warrants	2,514
Non-cash capital lease	$ 410