As of December 31, 2019 and 2018, the estimated fair value of our short-term and long-term marketable securities, classified as available for sale, are as follows (in thousands):



December 31, 2019	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate bonds	$	210,891	$	142	$	(27	)	$	211,006
U.S. government treasury bonds	70,587		65		$	(2	)	70,650
U.S. government agency bonds	22,085		17		(1		)	22,101
Commercial paper	14,426		—		—			14,426
Certificates of deposit	19		—		—			19
Total marketable securities, short-term	$	318,008	$	224	$	(30	)	$	318,202



December 31, 2018	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate bonds	$	45,100	$	—	$	(48	)	$	45,052
U.S. government agency bonds	19,981		—		(77		)	19,904
Commercial paper	17,793		—		—			17,793
U.S. government treasury bonds	15,292		—		(1		)	15,291
Certificates of deposit	420		1		(1		)	420
Total marketable securities, short-term	$	98,586	$	1	$	(127	)	$	98,460



December 31, 2018	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Corporate bonds	$	4,957	$	5	$	(2	)	$	4,960
U.S. government agency bonds	1,399		8		—			1,407
U.S. government treasury bonds	2,235		9		—			2,244
Certificates of deposit	500		1		—			501
Total marketable securities, long-term	$	9,091	$	23	$	(2	)	$	9,112

Cash equivalents are not included in the tables above as the gross unrealized gains and losses are not material. We have no short-term or long-term marketable securities that have been in a continuous material unrealized loss position for greater than twelve months as of December 31, 2019 and 2018. Amounts reclassified to earnings from accumulated other comprehensive income (loss), net related to unrealized gains or losses were not material in 2019 and 2018. For the year ended December 31, 2019, 2018 and 2017, realized gains or losses were not material.

Our fixed-income securities investment portfolio consists of investments that can have a maximum effective maturity of up to 40 months on any individual security. The securities that we invest in are generally deemed to be low risk based on their credit ratings from the major rating agencies. The longer the duration of these securities, the more susceptible they are to changes in market interest rates and bond yields. As interest rates increase, those securities purchased at a lower yield show a mark-to-market unrealized loss. The unrealized losses are primarily due to changes in interest rates and credit spreads. We expect to realize the full value of all these investments upon maturity or sale. The weighted average remaining duration of these securities was approximately seven months and four months as of December 31, 2019 and 2018, respectively.

As the carrying value approximates the fair value for our short-term and long-term marketable securities shown in the tables above, the following table summarizes the fair value of our short-term and long-term marketable securities classified by contractual maturity as of December 31, 2019 and 2018 (in thousands):



	December 31,
	2019		2018
Maturities within one year	$	318,202	$	98,460
Due in greater than one year	—		9,112
Total available for sale short-term and long-term marketable securities	$	318,202	$	107,572



	December 31,
	2019		2018
Equity securities under the equity method investment ¹	$	—	$	45,913
Equity securities without readily determinable fair values ²	$	5,887	$	9,862



Description	Balance as of December 31, 2019		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	236,923	$	236,923	$	—	$	—
Short-term investments:
Corporate bonds	211,006		—		211,006		—
Commercial paper	14,426		—		14,426		—
U.S. government agency bonds	22,101		—		22,101		—
U.S. government treasury bonds	70,650		70,650		—		—
Certificates of deposit	19		—		19		—
Prepaid expenses and other current assets:
Israeli funds	3,226		—		3,226		—
Current unsecured promissory note	25,005		—		—		25,005
Other Assets:
Long term unsecured promissory note	7,328		—		—		7,328
	$	590,684	$	307,573	$	250,778	$	32,333



Description	Balance as of December 31, 2018		Level 1		Level 2
Cash equivalents:
Money market funds	$	431,081	$	431,081	$	—
Commercial paper	4,681		—		4,681
Corporate bonds	3,880		—		3,880
U.S. government treasury bonds	2,195		2,195		—
Short-term investments:
Corporate bonds	45,052		—		17,793
Commercial paper	17,793		—		45,052
U.S. government agency bonds	19,904		—		19,904
U.S. government treasury bonds	15,291		15,291		—
Certificates of deposit	420		—		420
Long-term investments:
Corporate bonds	4,960		—		4,960
U.S. government agency bonds	1,407		—		1,407
U.S. government treasury bonds	2,244		2,244
Certificates of deposit	501		—		501
Prepaid expenses and other current assets:
Israeli funds	3,047		—		3,047
	$	552,456	$	450,811	$	101,645

Our investments in equity securities is considered Level 3 in the fair value hierarchy since the investments are in private companies without quoted market prices and we adjust the carrying value based on observable price changes.

The unsecured promissory note that was entered into in 2019 is classified as Level 3 in our fair value hierarchy as financial information of third parties may not be timely available and consequently we estimate the fair value based on the best available information at the measurement date. The original amount of the note was $54.2 million which decreased over 2019 due to payments received. Refer to Note 5 “Equity Method Investments” of the Notes to Consolidated Financial Statements for more information.

We enter into foreign currency forward contracts to minimize the short-term impact of foreign currency exchange rate fluctuations on certain trade and intercompany receivables and payables. These forward contracts are classified within Level 2 of the fair value hierarchy. The net gain from the settlement of foreign currency forward contracts during the year ended December 31, 2019 and 2018 was $3.2 million and $9.9 million, respectively. As of December 31, 2019 and 2018, the fair value of foreign exchange forward contracts outstanding was not material.



	December 31, 2019
	Local Currency Amount	Notional Contract Amount (USD)
Euro	€97,000	$	108,870
Chinese Yuan	¥431,000	60,702
Canadian Dollar	C$52,000	39,802
Israeli Shekel	ILS63,700	18,439
British Pound	£28,000	36,770
Japanese Yen	¥3,000,000	27,604
Brazilian Real	R$130,000	32,185
Mexican Peso	M$140,000	7,398
Australian Dollar	A$3,000	2,101
		$	333,871



	December 31, 2018
	Local Currency Amount	Notional Contract Amount (USD)
Euro	€62,000	$	71,095
Chinese Yuan	¥375,000	54,515
Brazilian Real	R$81,000	20,858
Canadian Dollar	C$27,000	19,808
British Pound	£13,000	16,635
Japanese Yen	¥1,700,000	15,357
Australian Dollar	A$3,000	2,114
		$	200,382