Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2015

Fair Value Disclosures [Abstract]

Schedule of Fair Value Financial Assets and Liabilities Measured on Recurring Basis

 The following table sets forth the fair value of the Company’s financial assets and liabilities measured on a recurring basis by level within the fair value hierarchy:

	September 30, 2015
	Level 1		Level 2		Level 3		Total
	(in thousands)
Financial Assets
Money market funds	$	155,766	$	—	$	—	$	155,766
Restricted money market funds		225		—		—		225
Total financial assets	$	155,991	$	—	$	—	$	155,991
	December 31, 2014
	Level 1		Level 2		Level 3		Total
	(in thousands)
Financial Assets
Money market funds	$	27,847	$	—	$	—	$	27,847
Restricted money market funds		75		—		—		75
Short-term investments		—		10,010		—		10,010
Total financial assets	$	27,922	$	10,010	$	—	$	37,932
Financial Liabilities
Preferred stock warrant liabilities	$	—	$	—	$	1,810	$	1,810

Schedule of Remeasured Preferred Stock Warrants to Fair Value using OPM and/or PWERM Models

At December 31, 2014, the Company remeasured the preferred stock warrants to fair value using the OPM and/or the PWERM models with the following assumptions used in the OPM:

	As of December 31, 2014
Expected term (in years)		1.2 – 2.5
Expected volatility		69 – 86	%
Risk-free interest rate		0.3 – 0.6	%
Expected dividend rate		—	%
Discount for lack of marketability		19.5 – 24.3	%

Summary of Changes in Estimated Fair Value of Preferred Stock Warrants Measured at Fair Value on Recurring Basis

The following table provides a summary of the changes in the estimated fair value of the Company’s preferred stock warrants, which were measured at fair value on a recurring basis until their exercise (in thousands):

Balance as of December 31, 2014	$	1,810
Fair value of preferred stock warrants exercised		(19,253	)
Change in fair value of preferred stock warrants		17,443
Balance as of September 30, 2015	$	—