We invest surplus funds in excess of operational requirements in a diversified portfolio of marketable securities, with the objectives of delivering competitive returns, maintaining a high degree of liquidity, and seeking to avoid the permanent impairment of principal.

Marketable securities as of March 31, 2024 and December 31, 2023 consisted of the following (in thousands):

		March 31, 2024
		Cost or Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Marketable equity securities
Equity securities	$	52,576	$	5,189	$	(4,094	)	$	53,671
Marketable debt securities
U.S. treasury securities		45,480		732		—			46,212
Corporate bonds		28,410		973		(298	)		29,085
Total marketable debt securities		73,890		1,705		(298	)		75,297
	$	126,466	$	6,894	$	(4,392	)	$	128,968

		December 31, 2023
		Cost or Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Marketable equity securities
Equity securities	$	59,228	$	7,896	$	(4,146	)	$	62,978
Marketable debt securities
U.S. treasury securities		53,662		1,307		(3	)		54,966
Corporate bonds		19,422		472		(197	)		19,697
Total marketable debt securities		73,084		1,779		(200	)		74,663
	$	132,312	$	9,675	$	(4,346	)	$	137,641

The amortized costs and fair value of our marketable debt securities, by contractual maturity, as of March 31, 2024 (in thousands) are as follows:

		March 31, 2024
		Amortized Cost		Fair Value
Less than 1 year	$	33,622	$	34,340
1 to 5 years		40,268		40,957
Total	$	73,890	$	75,297

As of March 31, 2024, the fair value of corporate bonds with unrealized loss position was $8.8 million, with an aggregated loss of $0.3 million. There were no treasury securities with unrealized loss position. As of December 31, 2023, the fair value of available-for-sale debt securities in unrealized loss position for corporate bonds and U.S. treasury securities were $7.1 million and $2.7 million, respectively, with an aggregated loss of $0.2 million. For all available-for-sale debt securities that were in unrealized loss positions, we have determined that it is more likely than not we will hold the securities until maturity or a recovery of the cost basis. We had no credit-related impairment loss as of March 31, 2024 and December 31, 2023.

Our derivative instruments consisted of call and put options sold at their fair value as of the balance sheet date. These derivative instruments are reported as Other current liabilities on our Condensed Consolidated Balance Sheets as of March 31, 2024 and December 31, 2023 (in thousands):

		March 31, 2024
		Cost		Unrealized Losses			Fair Value
Derivative instruments	$	8,097	$	(3,685	)	$	4,412
	$	8,097	$	(3,685	)	$	4,412

		December 31, 2023
		Cost		Unrealized Losses			Fair Value
Derivative instruments	$	8,797	$	(867	)	$	7,930
	$	8,797	$	(867	)	$	7,930

A summary of realized and unrealized gains and losses from our equity securities and derivative instruments are as follows (in thousands):

		Three Months Ended March 31,
		2024			2023
Net unrealized gains (losses) recognized on marketable equity securities	$	(2,655	)	$	2,014
Net realized gains (losses) recognized on marketable equity securities		5,479			1,669
Net unrealized gains (losses) recognized on derivative instruments		2,818			(102	)
Net realized gains recognized on derivative instruments		(218	)		717
Net realized gains recognized on marketable debt securities		(135	)		—
Total net gains (losses) recognized in interest and other income (loss), net	$	5,289		$	4,298

Our financial instruments measured at fair value on a recurring basis consisted of money-market funds, mutual funds, equity securities, corporate debt securities and derivatives. Equity securities are classified within Level 1 of the fair value hierarchy as they are valued based on quoted market price in an active market. Corporate debt securities and derivative instruments are valued based on quoted prices in markets that are less active, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency are generally classified within Level 2 of the fair value hierarchy.

Financial instruments valued based on unobservable inputs which reflect the reporting entity’s own assumptions or data that market participants would use in valuing an instrument are generally classified within Level 3 of the fair value hierarchy. We did not hold Level 3 financial instruments as of March 31, 2024, and December 31, 2023.

Financial instruments measured at fair value on a recurring basis as of March 31, 2024 and December 31, 2023 are classified based on the valuation technique in the table below (in thousands):

		March 31, 2024
		Fair Value Measurements Using
		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets:
U.S. treasury securities	$	46,212	$	—	$	—	$	46,212
Equity securities		53,671		—		—		53,671
Corporate bonds		—		29,086		—		29,086
Total assets at fair value	$	99,883	$	29,086	$	—	$	128,969

Liabilities
Derivative instruments	$	—	$	4,412	$	—	$	4,412
Total liabilities at fair value	$	—	$	4,412	$	—	$	4,412

		December 31, 2023
		Fair Value Measurements Using
		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets:
U.S. treasury securities	$	54,966	$	—	$	—	$	54,966
Equity securities		62,977		—		—		62,977
Corporate bonds		—		19,697		—		19,697
Total assets at fair value	$	117,943	$	19,697	$	—	$	137,640

Liabilities
Derivative instruments	$	—	$	7,930	$	—	$	7,930
Total liabilities at fair value	$	—	$	7,930	$	—	$	7,930