Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2021

Investments, Debt and Equity Securities [Abstract]

Schedule of Carrying Amounts and Fair Values of Debt Securities

Debt securities are classified as available-for-sale and reported under marketable securities in the condensed consolidated balance sheets. The following table summarizes carrying amounts and fair values as of September 30, 2021 and December 31, 2020 (in thousands):

	September 30, 2021
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Debt Securities:
U.S. treasury securities	$	97,587	$	14	$	(6)	$	97,595
Corporate debt securities	45,403		6		(34)		45,375
Total	$	142,990	$	20	$	(40)	$	142,970

	December 31, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
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	$	138,747	$	416	$	(5)	$	139,158

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

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

	September 30, 2021
	Amortized Cost		Fair Value
Due within one year	$	68,687	$	68,693
Due after one year but within five years	74,303		74,277
Total	$	142,990	$	142,970

Schedule Of Equity Investments

The types of equity investments are summarized in the following table (in thousands):

		Condensed Consolidated Balance Sheets Classification	September 30, 2021		December 31, 2020
Type	Description
Marketable equity investments	Money market funds	Cash and cash equivalents	$	1,140,671	$	56,474
Marketable equity investments	Corporate debt securities	Cash and cash equivalents	3,000		—
Marketable equity investments	Term bond mutual funds	Marketable securities	3,622		3,575
Non-marketable equity investments	Investments in equity securities without a readily determinable fair value	Other assets	367		517
			$	1,147,660	$	60,566

Summary of Realized and Unrealized Gains

The following table summarizes the realized and unrealized gains recognized in the condensed consolidated statements of operations for the term bond mutual funds during the three and nine months ended September 30, 2021 and 2020 (amounts in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Net gains recognized on marketable equity investments	$	35	$	107	$	100	$	44
Unrealized gains at the end of the period	$	35	$	107	$	100	$	44