Convertible Preferred Stock Warrant Liability (Tables)

12 Months Ended

Dec. 31, 2012

Estimated Fair Value for Each of the Convertible Preferred Stock Warrants

The following table sets forth the estimated fair value for each of the convertible preferred stock warrants as of December 31, 2011 and 2012 (in thousands, except share and per share data):

				Shares as of				Estimated Fair Value
Preferred Stock	Expiration Date	Exercise Price Per Share		December 31, 2011		December 31, 2012		December 31, 2011		December 31, 2012
Series A	Later of: (i) January 20, 2015 or (ii) 3 years after the closing of an initial public offering of our common stock	$	10.00		4,740		4,740	$	42	$	36
Series B	Later of: (i) September 28, 2016 or (ii) 5 years after the closing of an initial public offering of our common stock	$	13.10		76,335		76,335		724		647
Total					81,075		81,075	$	766	$	683