Investments (Tables)

6 Months Ended

Jun. 30, 2022

Schedule of Investments [Abstract]

Summary of Fair Value of Available-for-Sale Investments by Type of Security

The fair value of available-for-sale investments by type of security was as follows:

	June 30, 2022
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Investments:
U.S. treasury bills	$	332,729	$	—	$	(4,150	)	$	328,579
U.S. agency securities		165,061		—		(1,462	)		163,599
Total investments with a maturity of one year or less		497,790		—		(5,612	)		492,178
U.S. treasury bills		154,076		—		(3,775	)		150,301
U.S. agency securities		90,294		—		(2,519	)		87,775
Total investments with a maturity of one to two years		244,370		—		(6,294	)		238,076
Total investments	$	742,160	$	—	$	(11,906	)	$	730,254

	December 31, 2021
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Investments:
U.S. treasury bills	$	189,406	$	—	$	(228	)	$	189,178
U.S. agency securities		108,895		—		(138	)		108,757
Total investments with a maturity of one year or less		298,301		—		(366	)		297,935
U.S. treasury bills		280,743		—		(535	)		280,208
U.S. agency securities		99,998		—		(187	)		99,811
Total investments with a maturity of one to two years		380,741		—		(722	)		380,019
Total investments	$	679,042	$	—	$	(1,088	)	$	677,954

Available-for-sale Debt Securities in an Unrealized Loss Position

The following table summarizes our available-for-sale debt securities in an unrealized loss position for which an allowance for credit losses has not been recorded at June 30, 2022, aggregated by major security type and length of time in a continuous unrealized loss position (in thousands):

	Less than 12 Months					12 Months or Longer				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. treasury bills	$	478,880	$	(7,925	)	$	—	$	—	$	478,880	$	(7,925	)
U.S. agency securities		251,374		(3,981	)		—		—		251,374		(3,981	)
Total	$	730,254	$	(11,906	)	$	—	$	—	$	730,254	$	(11,906	)

The following table summarizes our available-for-sale debt securities in an unrealized loss position for which an allowance for credit losses has not been recorded at December 31, 2021, aggregated by major security type and length of time in a continuous unrealized loss position (in thousands):

	Less than 12 Months					12 Months or Longer				Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. treasury bills	$	469,386	$	(763	)	$	—	$	—	$	469,386	$	(763	)
U.S. agency securities		208,568		(325	)		—		—		208,568		(325	)
Total	$	677,954	$	(1,088	)	$	—	$	—	$	677,954	$	(1,088	)