Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value of Financial Assets by Level

The following tables summarize the amortized costs, unrealized gains and losses, and fair values of these financial assets by significant investment category and their levels within the fair value hierarchy (in thousands):

	December 31, 2021
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value		Level I		Level II		Level III
Financial Assets:
Cash Equivalents:
Money market funds	$	221,382	$	—	$	—	$	221,382	$	221,382	$	—	$	—
Marketable Securities:
Commercial paper	141,274		—		—		141,274		—		141,274		—
Certificates of deposits (1)	44,931		—		—		44,931		—		44,931		—
U.S. government notes	1,060,716		3		(2,909)		1,057,810		1,057,810		—		—
Corporate bonds	1,255,149		105		(3,028)		1,252,226		—		1,252,226		—
Agency securities	291,558		36		(333)		291,261		—		291,261		—
	2,793,628		144		(6,270)		2,787,502		1,057,810		1,729,692		—
Other Assets:
Money market funds - restricted	4,237		—		—		4,237		4,237		—		—
Total Financial Assets	$	3,019,247	$	144	$	(6,270)	$	3,013,121	$	1,283,429	$	1,729,692	$	—
____________________
(1) As of December 31, 2021, all of our certificates of deposits were domestic deposits.

	December 31, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value		Level I		Level II		Level III
Financial Assets:
Cash Equivalents:
Money market funds	$	438,854	$	—	$	—	$	438,854	$	438,854	$	—	$	—
Marketable Securities:
Commercial paper	51,211		—		—		51,211		—		51,211		—
Certificates of deposits (1)	50,136		3		—		50,139		—		50,139		—
U.S. government notes	523,320		187		(1)		523,506		523,506		—		—
Corporate bonds	878,484		1,167		(330)		879,321		—		879,321		—
Agency securities	475,132		343		(3)		475,472		—		475,472		—
	1,978,283		1,700		(334)		1,979,649		523,506		1,456,143		—
Other Assets:
Money market funds - restricted	4,235		—		—		4,235		4,235		—		—
Total Financial Assets	$	2,421,372	$	1,700	$	(334)	$	2,422,738	$	966,595	$	1,456,143	$	—
____________________
(1) As of December 31, 2020, all of our certificates of deposits were domestic deposits.

Fair Value of Available-for-sale Marketable Securities by Remaining Contractual Maturity

The fair values of available-for-sale marketable securities, by remaining contractual maturity, are as follows (in thousands):

	December 31, 2021
Due in 1 year or less	$	1,691,472
Due in 1 year through 2 years	1,096,030
Total marketable securities	$	2,787,502