Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Schedule of Fair Value Measurements of Financial Assets and Liabilities

The following table details the fair value measurements within the fair value hierarchy of the Company’s financial assets and liabilities at March 31, 2020 and December 31, 2019:

	March 31, 2020
	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents and investments:
Money market funds	$	43,772	$	—	$	—	$	43,772
Commercial paper		—		83,100		—		83,100
Corporate bonds		—		120,201		—		120,201
U.S. Treasury securities		—		677,310		—		677,310
Restricted cash:
Certificates of deposit		—		552		—		552
Money market funds		—		3,029		—		3,029
Total	$	43,772	$	884,192	$	—	$	927,964

	December 31, 2019
	Level 1		Level 2		Level 3		Total
	(in thousands)
Cash equivalents and investments:
Money market funds	$	96,618	$	—	$	—	$	96,618
Commercial paper		—		87,185		—		87,185
Corporate bonds		—		87,138		—		87,138
U.S. Treasury securities		—		631,174		—		631,174
Restricted cash:
Certificates of deposit		—		5,816		—		5,816
Money market funds		—		3,029		—		3,029
Total	$	96,618	$	814,342	$	—	$	910,960

Summary of Composition of Short and Long Term Investments

The following tables summarize the composition of our short- and long-term investments at March 31, 2020 and December 31, 2019.

	March 31, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
	(in thousands)
Commercial paper	$	83,100	$	—	$	—		$	83,100
Corporate bonds		120,639		234		(672	)		120,201
U.S. Treasury securities		600,897		1,422		(8	)		602,311
Total	$	804,636	$	1,656	$	(680	)	$	805,612

	December 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Fair Value
	(in thousands)
Commercial paper	$	77,214	$	—	$	—		$	77,214
Corporate bonds		86,900		251		(13	)		87,138
U.S. Treasury securities		581,066		207		(15	)		581,258
Total	$	745,180	$	458	$	(28	)	$	745,610

Summary of Contractual Maturities of Short and Long Term Investments

The contractual maturities of short-term and long-term investments held at March 31, 2020 and December 31, 2019 are as follows:

	March 31, 2020				December 31, 2019
	Amortized Cost Basis		Aggregate Fair Value		Amortized Cost Basis		Aggregate Fair Value
	(in thousands)				(in thousands)
Due within one year	$	737,992	$	739,428	$	691,556	$	691,834
Due after 1 year through 2 years		66,644		66,184		53,624		53,776
Total	$	804,636	$	805,612	$	745,180	$	745,610