Net Loss per Share of Common Stock (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		0 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jul. 02, 2013 IPO - conversion of mandatorily redeemable convertible preferred stock, Series F Common Stock	Jun. 30, 2013 Pro Forma	Jun. 30, 2013 Pro Forma
Pro Forma Net Loss Per Common Share
Shares of common stock issued on conversion related to the ratchet provision					1,584,863
Numerator (in thousands):
Numerator for basic and diluted net loss per share attributable to common stockholders (in dollars)	$ (273)	$ (4,780)	$ (5,432)	$ (13,907)		$ (15,986)	$ (21,145)
Plus: mark-to-market income	136		136
Plus: Series F Preferred Stock deemed dividend	$ (15,849)		$ (15,849)
Denominator:
Denominator for basic and diluted net loss per share attributable to common stockholders - weighted average shares	7,760,494	7,389,173	7,744,943	7,460,025		49,432,810	49,417,259
Plus: conversion of preferred stock to common stock	34,172,316		34,172,316
Plus: newly issued IPO shares	7,500,000		7,500,000
Basic and diluted net loss per share attributable to common stockholders	$ (0.04)	$ (0.65)	$ (0.70)	$ (1.86)		$ (0.32)	$ (0.43)