Fair Value Of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2012

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value on a Recurring Basis

Assets and liabilities measured at fair value on a recurring basis include the following as of September 30, 2012 and December 31, 2011 (in thousands):

	September 30, 2012								December 31, 2011
	Fair Value		Level 1		Level 2		Level 3		Fair Value		Level 1		Level 2		Level 3
Cash equivalents	$	51,521	$	51,521	$	—	$	—	$	71,521	$	71,521	$	—	$	—

Changes in Fair Value of Preferred Stock Warrant Liability

The following table summarizes the changes in the fair value of preferred stock warrant liability for the nine months ended September 30, 2011 (in thousands):

Fair Value at December 31, 2010	$	39,756
Changes in fair value of preferred stock warrant liabilities recorded in the statement of operations	42,559
Exercise of preferred stock warrants	(82,315		)
Fair Value at September 30, 2011	$	—