Fair Value Measurements

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

The Company measures and reports its cash equivalents and restricted cash at fair value. 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:

	December 31, 2016
	Level 1		Level 2		Level 3		Total
	(in thousands)
Financial Assets
Money market funds	$	107,043	$	—	$	—	$	107,043
Restricted money market funds		200		—		—		200
Total financial assets	$	107,243	$	—	$	—	$	107,243

	December 31, 2015
	Level 1		Level 2		Level 3		Total
	(in thousands)
Financial Assets
Money market funds	$	148,604	$	—	$	—	$	148,604
Restricted money market funds		225		—		—		225
Total financial assets	$	148,829	$	—	$	—	$	148,829

Money market funds and restricted money market funds are measured at fair value on a recurring basis using quoted prices and are classified as a Level 1 input.

During the years ended December 31, 2015 and 2014, the Company’s preferred stock warrant liabilities contained unobservable inputs that reflected the Company’s own assumptions in which there was little, if any, market activity for at the measurement date. Accordingly, the Company’s warrant liabilities were measured at fair value on a recurring basis using unobservable inputs until the warrants were exercised in 2015. The warrant liabilities were classified as Level 3 inputs.

There were no transfers between Levels 1, 2 or 3 during the year ended December 31, 2016. During the year ended December 31, 2015, $10.0 million of short-term investments transferred from being a Level 2 financial asset to a Level 1 financial asset when the short-term investments were sold in July 2015. The proceeds from the sale of the short-term investments were invested in money market funds, which is a Level 1 financial asset. The Company realized a $10,000 other-than-temporary impairment loss on its short-term investments through other income (expense) in the accompanying consolidated statements of operations.

The following table provides a summary of the changes in the estimated fair value of the Company’s preferred stock warrant liabilities, which were measured at fair value on a recurring basis using unobservable inputs (Level 3) until their exercise in 2015 (in thousands):

	December 31, 2015
	(in thousands)
Fair value, beginning balance	$	1,810
Fair value of preferred stock warrants exercised		(19,253	)
Change in fair value of preferred stock warrants		17,443
Fair value, ending balance	$	—

The change in fair value of the preferred stock warrant liabilities was attributable to the increase of the fair value of the underlying stock. The change in the fair value of preferred stock warrants for each presented period is recognized as a component of other income (expense), net in the consolidated statements of operations.