Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2017

Fair Value Measurements

Assets and liabilities measured at fair value on a recurring basis

Assets and liabilities measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016 are as follows:

			Quoted Prices		Significant
			in Active		Other		Significant
			Markets for		Observable		Unobservable
			Identical Assets		Inputs		Inputs
Assets	Total		(Level 1)		(Level 2)		(Level 3)
March 31, 2017	(in thousands)
Money market funds included in cash and cash equivalents	$	41,973	$	41,973	$	—	$	—
Marketable securities:
U.S. Treasury notes		114,066		114,066		—		—
Equity securities		2,000		2,000		—		—
Total marketable securities	$	116,066	$	116,066	$	—	$	—
Warrants to purchase equity securities		1,141		—		1,141		—
Total	$	159,180	$	158,039	$	1,141	$	—
December 31, 2016
Money market funds included in cash and cash equivalents	$	36,003	$	36,003	$	—	$	—
Marketable securities:
U.S. Treasury notes		130,173		130,173		—		—
U.S. Government agency securities		7,604		—		7,604		—
Equity securities		1,360		1,360		—		—
Total marketable securities	$	139,137	$	131,533	$	7,604	$	—
Warrants to purchase equity securities		792		—		792		—
Total	$	175,932	$	167,536	$	8,396	$	—

Assumptions

The assumptions utilized to value the warrants to purchase equity securities as of March 31, 2017 and December 31, 2016 are as follows:

	As of March 31,		As of December 31,
	2017		2016
Risk-free interest rate	1.8	%	1.8	%
Expected dividend yield	—	%	—	%
Expected term (in years)	4.4		4.7
Expected volatility	86.7	%	97.5	%