Marketable Securities and Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2020

Investments, All Other Investments [Abstract]

Schedule of Marketable Securities

The following tables present marketable securities by contractual maturity and security type:

As of June 30, 2020 (in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Due within one year:
U.S. government securities	$	454,878	$	75	$	(63)	$	454,890
Due after one year through five years:
U.S. government securities	21,451		—		(20)		21,431
Total	$	476,329	$	75	$	(83)	$	476,321

As of December 31, 2019 (in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Due within one year:
Commercial paper	$	314,292	$	74	$	(23)	$	314,343
U.S. government securities	78,612		48		(3)		78,657
Certificates of deposit	66,241		17		(2)		66,256
Total	$	459,145	$	139	$	(28)	$	459,256

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

The following tables present information about the Company's financial assets measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values:

As of June 30, 2020 (in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	120,776	$	—	$	120,776
U.S. government securities	—		20,600		—		20,600
Marketable securities:
U.S. government securities	—		476,321		—		476,321
Total	$	—	$	617,697	$	—	$	617,697

As of December 31, 2019 (in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	28,192	$	—	$	28,192
Certificates of deposit	—		20,500		—		20,500
Marketable securities:
Commercial paper	—		314,343		—		314,343
U.S. government securities	—		78,657		—		78,657
Certificates of deposit	—		66,256		—		66,256
Total	$	—	$	507,948	$	—	$	507,948