Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2013

Fair Value of Financial Assets and Liabilities Measured at Fair Value and Classification by Level of Input

The following tables summarize the fair value of financial assets and liabilities (investments and convertible preferred stock warrant liabilities) that are measured at fair value and the classification by level of input within the fair value hierarchy:

	Fair Value Measurements as of
	September 30, 2013
(in thousands)	Level 1		Level 2		Level 3		Total
Investments:
Money market funds	$	22,831	$	—	$	—	$	22,831
Federal agency securities		—		17,925		—		17,925
Commercial paper		—		11,750		—		11,750
Corporate debt securities		—		1,969		—		1,969
Total investments	$	22,831	$	31,644	$	—	$	54,475
	Fair Value Measurements as of
	December 31, 2012
(in thousands)	Level 1		Level 2		Level 3		Total
Investments:
Money market funds	$	5,923	$	—	$	—	$	5,923
Federal agency securities		—		9,351		—		9,351
Total investments	$	5,923	$	9,351	$	—	$	15,274
Convertible preferred stock warrant liabilities	$	—	$	—	$	157	$	157

Fair Value of Convertible Preferred Stock Warrant Liability

The following table presents changes in financial instruments measured at fair value using Level 3 inputs:

	Convertible
	Preferred Stock
	Warrant
	Liabilities
	(in thousands)
Balance at December 31, 2012	$	157
Reclassification of preferred stock warrant liabilities to additional paid-in capital in conjunction with the conversion of the convertible preferred stock into common stock upon the closing of the Company’s IPO		(157	)
Balance at September 30, 2013	$	—