Investments (Tables)

6 Months Ended

Jun. 30, 2020

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):

	June 30, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
U.S. Treasury notes	$	185,739	$	656	$	—		$	186,395
Government sponsored enterprise securities		38,445		111		—			38,556
Corporate debt securities		90,142		567		(1	)		90,708
Commercial paper		32,317		134		—			32,451
	$	346,643	$	1,468	$	(1	)	$	348,110

	December 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses			Estimated Fair Value
U.S. Treasury notes	$	228,609	$	7	$	(13	)	$	228,603
Government sponsored enterprise securities		88,920		5		(30	)		88,895
Corporate debt securities		87,785		262		(8	)		88,039
Commercial paper		102,151		61		—			102,212
	$	507,465	$	335	$	(51	)	$	507,749

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 June 30, 2020 and December 31, 2019, 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
June 30, 2020
Corporate debt securities	$	—	$	—		$	4,003	$	(1	)	$	4,003	$	(1	)
Total	$	—	$	—		$	4,003	$	(1	)	$	4,003	$	(1	)

	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, 2019:
U.S. Treasury notes	$	148,397	$	(13	)	$	—	$	—		$	148,397	$	(13	)
Government sponsored enterprise securities		61,103		(30	)		—		—			61,103		(30	)
Corporate debt securities		11,334		(8	)		—		—			11,334		(8	)
Total	$	220,834	$	(51	)	$	—	$	—		$	220,834	$	(51	)