Condensed Consolidated Statements of Comprehensive Loss (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement [Abstract]
Revenue	$ 7,218	$ 5,943	$ 12,894	$ 10,445
Costs and expenses:
Cost of revenue	3,522	3,334	6,404	5,990
Research and development	3,626	2,971	6,685	5,168
Selling, general and administrative	6,708	3,251	12,834	6,418
Total costs and expenses	13,856	9,556	25,923	17,576
Loss from operations	(6,638)	(3,613)	(13,029)	(7,131)
Other income (expense):
Interest income	3	6	6	13
Interest expense	(489)	(220)	(874)	(332)
Other income (expense)	(9)	185	(13)	172
Revaluation of preferred stock warrant liability	1,638	71	1,156	97
Total other income (expense)	1,143	42	275	(50)
Net loss	(5,495)	(3,571)	(12,754)	(7,181)
Accretion of mandatorily redeemable convertible preferred stock	(2,311)	(1,844)	(4,653)	(3,637)
Net loss attributable to common stockholders	$ (7,806)	$ (5,415)	$ (17,407)	$ (10,818)
Net loss per share-basic and diluted	$ (13.69)	$ (16.02)	$ (31.48)	$ (32.49)
Shares used in computing basic and diluted net loss per share	570	338	553	333