Marketable Securities

12 Months Ended

Dec. 31, 2019

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 December 31, 2019 and 2018 at net book value:

	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In thousands)
Marketable securities:
U.S. Treasury securities	$	159,361	$	142	$	(1	)	$	159,502
Financial institution debt securities		40,173		105		-			40,278
Corporate debt securities		18,966		1		-			18,967
Other asset-backed securities		8,485		14		-			8,499
Total	$	226,985	$	262	$	(1	)	$	227,246
	December 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(In thousands)
Marketable securities:
U.S. Treasury securities	$	165,959	$	2	$	(13	)	$	165,948
Financial institution debt securities		65,436		1		(17	)		65,420
Corporate debt securities		23,836		-		(1	)		23,835
Total	$	255,231	$	3	$	(31	)	$	255,203

The amortized cost of available-for-sale securities is adjusted for amortization of premiums and accretion of discounts to maturity. At December 31, 2019 and 2018, the balance in the Company’s accumulated other comprehensive income (loss) was composed of activity related to the Company’s available-for-sale marketable securities. There were no material realized gains or losses in the years ended December 31, 2019, 2018 or 2017 and, as a result, the Company did not reclassify any amounts out of accumulated other comprehensive income (loss) during these periods. The Company did not have any securities in a material unrealized loss position at December 31, 2019 or 2018.

The Company's available-for-sale securities that are classified as short term marketable securities in the 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 consolidated balance sheet mature after one year but within five years from the balance sheet date. At December 31, 2019 and 2018, the Company did not hold any investments that matured beyond five years.