Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2020

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value on a Recurring Basis

The following tables summarize the Company’s financial assets measured at fair value on a recurring basis by level within the fair value hierarchy:

	September 30, 2020
	Fair Value Hierarchy	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Market Value
	(In thousands)
Money market funds	Level 1	$	65,472	$	—	$	—		$	65,472
U.S. government treasury securities	Level 1		363,248		1,080		(7	)		364,321
Commercial paper	Level 2		4,984		—		—			4,984
Corporate bonds	Level 2		10,010		21		—			10,031
Total cash equivalents and marketable    securities		$	443,714	$	1,101	$	(7	)	$	444,808
	December 31, 2019
	Fair Value Hierarchy	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Market Value
	(In thousands)
Money market funds	Level 1	$	61,104	$	—	$	—		$	61,104
U.S. government treasury securities	Level 1		227,446		149		(8	)		227,587
Commercial paper	Level 2		43,735		—		—			43,735
Corporate bonds	Level 2		10,103		3		(2	)		10,104
Total cash equivalents and marketable    securities		$	342,388	$	152	$	(10	)	$	342,530