Fair Value of Financial Measurements (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value of Assets and Liabilities Measured on Recurring Basis

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy:

	Fair Value Measurements at
	December 31, 2016
	Total		Level 1		Level 2		Level 3
	(in thousands)
Assets:
Money market mutual funds (included in cash and cash equivalents)	$	20,698	$	20,698	$	—	$	—

Certificates of deposit	$	22,046	$	—	$	22,046	$	—
Agency bonds		5,913		—		5,913		—
United States Treasury securities		68,716		68,716		—		—
Short-term investments	$	96,675	$	68,716	$	27,959	$	—

	Fair Value Measurements at
	December 31, 2015
	Total		Level 1		Level 2		Level 3
	(in thousands)
Assets:
Certificates of deposit	$	16,160	$	—	$	16,160	$	—
Agency bonds		10,031		—		10,031		—
United States Treasury securities		5,047		5,047		—		—
Short-term investments	$	31,238	$	5,047	$	26,191	$	—

Schedule of Assumptions Used to Estimate Fair Value of Series AA Preferred Stock Warrants

The following table details the assumptions used in the Black-Scholes option pricing model used to estimate the fair value of the Series AA preferred stock warrants as of February 17, 2015, the date upon which the Series AA preferred stock warrants became exercisable for common stock:

	February 17,
	2015
Volatility		60%
Expected term (years)	8.4
Expected dividend yield		0.0%
Risk-free rate		1.7%

Schedule of Change in Company's Level 3 Liabilities

The following table reflects the change in the Company’s Level 3 liabilities for the year ended December 31, 2015:

	Convertible preferred stock warrant liabilities			Convertible Bridge Notes redemption rights derivative			2020 Convertible Notes derivative liability
	(in thousands)
Balance at December 31, 2014	$	482		$	480		$	—
Issuance of 2020 Convertible Notes		—			—			12,423
Change in fair value		(267	)		(480	)		42,793
Reclassification to stockholders’ equity		(215	)		—			—
Conversion to common stock		—			—			(55,216	)
Balance at December 31, 2015	$	—		$	—		$	—