Investments (Tables)

9 Months Ended

Sep. 30, 2021

Investments Debt And Equity Securities [Abstract]

Carrying Value and Amortized Cost of Company Investments Summarized by Major Security Type

The carrying value and amortized cost of the Company’s investments, summarized by major security type, consisted of the following (in thousands):

	September 30, 2021
	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
U.S. Treasury notes	$	179,885	$	4	$	(11	)	$	179,878
Government sponsored enterprise securities		56,018		—		(6	)		56,012
Municipal bonds		19,129		—		(7	)		19,122
Commercial paper		190,631		24		(16	)		190,639
	$	445,663	$	28	$	(40	)	$	445,651

	December 31, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses				Estimated Fair Value
U.S. Treasury notes	$	205,111	$	6	$	(27	)		$	205,090
Government sponsored enterprise securities		10,004		—		(5	)			9,999
Corporate debt securities		52,341		47		—		*		52,388
Commercial paper		38,443		21		(11	)			38,453
	$	305,899	$	74	$	(43	)		$	305,930

*	Unrealized loss was less than $500.

Summary of Gross Unrealized Losses and Fair Value of Available-For-Sale Investment Securities in Unrealized Loss Position

The following table presents gross unrealized losses and fair value for those available-for-sale investment securities that were in an unrealized loss position as of September 30, 2021 and December 31, 2020, aggregated by investment category and length of time that the individual securities have been in a continuous loss position (in thousands):

	Less Than 12 Months						12 Months or Greater				Total
	Estimated Fair Value		Unrealized Losses				Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
September 30, 2021
U.S. Treasury notes	$	105,515	$	(11	)		$	—	$	—	$	105,515	$	(11	)
Government sponsored enterprise securities		56,012		(6	)			—		—		56,012		(6	)
Municipal bonds		19,122		(7	)			—		—		19,122		(7	)
Commercial paper		76,688		(16	)			—		—		76,688		(16	)
Total	$	257,337	$	(40	)		$	—	$	—	$	257,337	$	(40	)

	Less Than 12 Months						12 Months or Greater				Total
	Estimated Fair Value		Unrealized Losses				Estimated Fair Value		Unrealized Losses		Estimated Fair Value		Unrealized Losses
December 31, 2020:
U.S. Treasury notes	$	129,631	$	(27	)		$	—	$	—	$	129,631	$	(27	)
Government sponsored enterprise securities		10,004		(5	)			—		—		10,004		(5	)
Corporate debt securities		6,252		—		*		—		—		6,252		—		*
Commercial paper		23,466		(11	)			—		—		23,466		(11	)
Total	$	169,353	$	(43	)		$	—	$	—	$	169,353	$	(43	)

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*	Unrealized loss was less than $500.