Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2020

Fair Value Disclosures [Abstract]

Schedule of Assets Measured at Fair Value on Recurring Basis

The following table presents the Company’s financial assets and liabilities measured at fair value on a recurring basis as of September 30, 2020 and December 31, 2019 (in thousands):

			Fair Value Measurements at Reporting Date Using
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of September 30, 2020:
Financial assets:
Money market funds	$	349,130	$	349,130	$	—	$	—
U.S. Treasury debt securities		49,573		49,573		—		—
Corporate debt securities		103,335		—		103,335		—
Total financial assets measured at fair value on a recurring basis	$	502,038	$	398,703	$	103,335	$	—
Financial liabilities:
Stock price appreciation milestones	$	27,644	$	—	$	—	$	27,644
Total financial liabilities measured at fair value on a recurring basis	$	27,644	$	—	$	—	$	27,644
As of December 31, 2019
Money market funds	$	84,814	$	84,814		—	$	—
U.S. Treasury debt securities		60,303		60,303		—		—
Corporate debt securities		100,750		—		100,750		—
Total financial assets measured at fair value on a recurring basis	$	245,867	$	145,117	$	100,750	$	—

Summary of Changes in The Fair Value of The Company’s Level 3 Enterprise Fair Value Milestone Payment Liability

The following table presents the changes in fair value of the Company’s Level 3 enterprise fair value milestone payment liability (in thousands):

Balance at December 31, 2019	$	—
Changes in fair value of stock price appreciation milestones liability		27,644
Balance at September 30, 2020	$	27,644