Marketable Securities

3 Months Ended

Mar. 31, 2021

Investments Debt And Equity Securities [Abstract]

Marketable Securities

3. Marketable Securities

The following table summarizes the Company’s available-for-sale marketable securities as of March 31, 2021 and December 31, 2020 at net book value:

	March 31, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In thousands)
Marketable securities:
U.S. Treasury and other government securities	$	204,473	$	49	$	(4	)	$	204,518
Financial institution debt securities		169,979		7		(45	)		169,941
Corporate debt securities		51,311		1		(13	)		51,299
Other asset-backed securities		33,509		1		(8	)		33,502
Total	$	459,272	$	58	$	(70	)	$	459,260
	December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In thousands)
Marketable securities:
U.S. Treasury and other government securities	$	245,666	$	13	$	(11	)	$	245,668
Financial institution debt securities		138,445		6		(8	)		138,443
Corporate debt securities		41,765		3		(2	)		41,766
Other asset-backed securities		11,474		1		(1	)		11,474
Total	$	437,350	$	23	$	(22	)	$	437,351

The amortized cost of available-for-sale securities is adjusted for amortization of premiums and accretion of discounts to maturity. At March 31, 2021 and December 31, 2020, the balance in the Company’s accumulated other comprehensive (loss) income was composed of activity related to the Company’s available-for-sale marketable securities. There were no realized gains or losses in the three months ended March 31, 2021 or for the year ended December 31, 2020. The Company did not reclassify any amounts out of accumulated other comprehensive (loss) income during this period. The Company did not have any securities in a material unrealized loss position at March 31, 2021 or December 31, 2020.

The Company's available-for-sale securities that are classified as short-term marketable securities in the condensed consolidated balance sheet mature within one year or less as of the balance sheet date. Available-for-sale securities that are classified as noncurrent in the condensed consolidated balance sheet are those that mature after one year but within five years from the balance sheet date and that the Company does not intend to dispose of within the next twelve months. At March 31, 2021 and December 31, 2020, the Company did not hold any investments that matured beyond five years of the balance sheet date.