Investments (Tables)

6 Months Ended

Jun. 30, 2021

Investments, Debt and Equity Securities [Abstract]

Our investments consisted of the following (in thousands):


	As of June 30, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Certificates of deposit	$	4,370	$	48	$	—	$	4,418

Corporate notes and bonds	577,356		2,190		(161)		579,385
U.S. Treasuries	82,148		7		(20)		82,135
U.S. Government agencies	200,500		9		(146)		200,363
Total	$	864,374	$	2,254	$	(327)	$	866,301


	As of December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Certificates of deposit	$	2,679	$	73	$	—	$	2,752
Commercial paper	19,994		—		—		19,994
Corporate notes and bonds	433,445		4,248		(41)		437,652
U.S. Treasuries	74,914		26		(6)		74,934
U.S. Government agencies	89,451		54		(13)		89,492
Total	$	620,483	$	4,401	$	(60)	$	624,824

Summary of Gross Unrealized Losses and Fair Value of Investments in a Continuous Unrealized Loss Position

The following tables present the gross unrealized losses and related fair values of our investments that have been in a continuous unrealized loss position (in thousands):


	As of June 30, 2021
	Less Than 12 Months				Greater Than 12 Months				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Certificates of deposit	$	490	$	—	$	—	$	—	$	490	$	—
Commercial paper	—		—		—		—		—		—
Corporate notes and bonds	267,699		(159)		17,902		(2)		285,601		(161)
U.S. Treasuries	70,599		(20)		—		—		70,599		(20)
U.S. Government agencies	159,570		(143)		2,497		(3)		162,067		(146)
Total	$	498,358	$	(322)	$	20,399	$	(5)	$	518,757	$	(327)


	As of December 31, 2020
	Less Than 12 Months				Greater Than 12 Months				Total
	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss

Commercial paper	$	4,997	$	—	$	—	$	—	$	4,997	$	—
Corporate notes and bonds	92,855		(41)		870		—		93,725		(41)
U.S. Treasuries	42,799		(6)		—		—		42,799		(6)
U.S. Government agencies	37,488		(13)		1,700		—		39,188		(13)
Total	$	178,139	$	(60)	$	2,570	$	—	$	180,709	$	(60)

Summary of Contractual Maturities of Investments

The following table summarizes the contractual maturities of our investments as of June 30, 2021 (in thousands):


	Amortized Cost		Fair Value
Due within one year	$	464,094	$	465,435
Due within one to three years	400,280		400,866
Total	$	864,374	$	866,301