SHORT-TERM AND LONG-TERM INVESTMENTS

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Short-term and long-term investments include marketable securities in the amount of $735,717 and $488,727 as of December 31, 2019 and 2018, respectively and short-term bank deposits in the amounts of $17,444 as of December 31, 2019.

The following table summarizes amortized costs, gross unrealized gains and losses and estimated fair values of available-for-sale marketable securities as of December 31, 2019 and 2018:


	Amortized cost						Gross unrealized gains						Gross unrealized losses				Estimated fair value (Level 2 within the fair value hierarchy)
	December 31,						December 31,						December 31,				December 31,
	2019		2018		2019		2018		2019		2018		2019		2018
Corporate debentures	$	687,886	$	457,944	$	4,865	$	190	$	(271)	$	(1,993)	$	692,480	$	456,141
U.S. Treasuries	23,182		21,943		82		—		(2)		(226)		23,262		21,717
U.S. Government Agencies	19,957		10,854		38		16		(20)		(1)		19,975		10,869
	$	731,025	$	490,741	$	4,985	$	206	$	(293)	$	(2,220)	$	735,717	$	488,727

The scheduled maturities of available-for-sale marketable securities as of December 31, 2019 are as follows:


	Amortized cost		Estimated fair value
Due within one year	$	192,882	$	193,328
Due after one year through five years	538,142		542,389
	$	731,025	$	735,717

Investments with continuous unrealized losses for less than 12 months and 12 months or greater and their related fair values as of December 31, 2019 and 2018 are as indicated in the following tables:


	December 31, 2019
	Investments with continuous unrealized losses for less than 12 months						Investments with continuous unrealized losses for 12 months or greater						Total Investments with continuous unrealized losses
	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Corporate debentures	$	70,733	$	(117)	$	48,658	$	(154)	$	119,391	$	(271)
U.S. Treasuries	—		—		5,005		(2)		5,005		(2)
U.S. Government Agencies	10,974		(20)		—		—		10,974		(20)
	$	81,707	$	(137)	$	53,663	$	(156)	$	135,370	$	(293)


	December 31, 2018
	Investments with continuous unrealized losses for less than 12 months						Investments with continuous unrealized losses for 12 months or greater						Total Investments with continuous unrealized losses
	Fair value		Unrealized losses		Fair value		Unrealized losses		Fair value		Unrealized losses
Corporate debentures	$	231,845	$	(754)	$	113,870	$	(1,239)	$	345,715	$	(1,993)
U.S. Treasuries	14,926		(12)		6,791		(214)		21,717		(226)
U.S. Government Agencies	7,932		(1)		—		—		7,932		(1)
	$	254,703	$	(767)	$	120,661	$	(1,453)	$	375,364	$	(2,220)