Cash Equivalents and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2021

Investments, Debt and Equity Securities [Abstract]

Schedule of Carrying Amounts and Fair Values of Debt Securities

Cash equivalents and available-for-sale debt securities consisted of the following as of December 31, 2021 and 2020 (in thousands):

	December 31, 2021
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Cash equivalents:
Money market funds	$	684,485	$	—	$	—	$	684,485
U.S. treasury securities	22,000		—		—		22,000
U.S. government agency securities	4,286		—		(1)		4,285
Corporate debt securities	15,998		—		—		15,998
Total cash equivalents	726,769		—		(1)		726,768
Debt securities:
U.S. treasury securities	442,715		2		(432)		442,285
U.S. government agency securities	75,725		—		(159)		75,566
Corporate debt securities	54,335		17		(175)		54,177
Total debt securities	572,775		19		(766)		572,028
Total cash equivalents and debt securities	$	1,299,544	$	19	$	(767)	$	1,298,796

	December 31, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Cash equivalents:
Money market funds	$	56,474	$	—	$	—	$	56,474
Debt Securities:
U.S. treasury securities	50,087		136		—		50,223
Corporate debt securities	85,413		265		(5)		85,673
Asset-backed securities	3,247		15		—		3,262
Total debt securities	138,747		416		(5)		139,158
Total cash equivalents and debt securities	$	195,221	$	416	$	(5)	$	195,632

Schedule of Amortized Costs and Fair Value of Debt Securities Based on Contractual Maturities

The amortized cost and fair value of the available-for-sale debt securities based on contractual maturities are as follows (in thousands):

	December 31, 2021
	Amortized Cost		Fair Value
Due within one year	$	392,629	$	392,412
Due after one year but within five years	180,146		179,616
Total	$	572,775	$	572,028

Summary of Realized and Unrealized Gains

The following table summarizes the realized and unrealized gains recognized in the consolidated

statements of operations for the term bond mutual funds during the years ended December 31, 2021, 2020, and 2019 (in thousands):

	Year Ended December 31,
	2021		2020		2019
Net gains recognized on marketable equity investments	$	132	$	107	$	582
Less: Net gains recognized on sale of marketable equity investments	—		—		(316)
Unrealized gains at the end of the period	$	132	$	107	$	266