Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Income Statement [Abstract]
Revenue	$ 8,751	$ 5,676
Costs and expenses:
Cost of revenue	4,325	2,882
Research and development	4,732	3,059
Selling, general and administrative	10,674	6,126
Total costs and expenses	19,731	12,067
Loss from operations	(10,980)	(6,391)
Other income (expense):
Interest income	64	3
Interest expense	(536)	(385)
Other expense	30	(4)
Revaluation of preferred stock warrant liability		(482)
Total other expense	(442)	(868)
Net loss	(11,422)	(7,259)
Accretion of mandatorily redeemable convertible preferred stock		(2,342)
Net loss attributable to common stockholders	$ (11,422)	$ (9,601)
Net loss per share - basic and diluted	$ (0.68)	$ (17.88)
Shares used in computing basic and diluted net loss per share	16,917	537