Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]
Revenue	$ 8,389	$ 6,035	$ 21,283	$ 16,480
Costs and expenses:
Cost of revenue	3,784	3,086	10,188	9,076
Research and development	3,784	3,085	10,469	8,253
Selling, general and administrative	7,988	4,170	20,822	10,588
Total costs and expenses	15,556	10,341	41,479	27,917
Loss from operations	(7,167)	(4,306)	(20,196)	(11,437)
Other income (expense):
Interest income	22	4	28	17
Interest expense	(538)	(219)	(1,412)	(551)
Other expense	(17)	(198)	(30)	(26)
Revaluation of preferred stock warrant liability		53	1,156	150
Total other income (expense)	(533)	(360)	(258)	(410)
Net loss	(7,700)	(4,666)	(20,454)	(11,847)
Accretion of mandatorily redeemable convertible preferred stock		(1,878)	(4,653)	(5,515)
Net loss attributable to common stockholders	$ (7,700)	$ (6,544)	$ (25,107)	$ (17,362)
Net loss per share - basic and diluted	$ (0.53)	$ (18.28)	$ (4.74)	$ (51.06)
Shares used in computing basic and diluted net loss per share	14,616	358	5,292	340