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.

We regularly review our investment portfolio to identify and evaluate investments that have indicators of possible impairment. Investments are considered impaired when a decline in fair value is judged to be other-than-temporary. If the cost of an individual investment exceeds its fair value, we evaluate, among other factors, general market conditions, the duration and

extent to which the fair value is less than cost, and our intent and ability to hold the investment. Once a decline in fair value is determined to be other-than-temporary, we will record an impairment charge and establish a new cost basis for the investment.


	December 31, 2022
	Cost or Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Mutual funds	$	26,352	$	—	$	(3,143)	$	23,209
U.S. treasury securities	25,640		182		(24)		25,798
Corporate bonds	13,496		48		(106)		13,438
Equity securities	53,273		2,776		(5,836)		50,213
	$	118,761	$	3,006	$	(9,109)	$	112,658


	December 31, 2021
	Cost or Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Mutual funds	$	50,000	$	—	$	(338)	$	49,662
Corporate bonds	6,996		290		—		7,286
Equity securities	38,100		—		(1,331)		36,769
	$	95,096	$	290	$	(1,669)	$	93,717


	December 31, 2022
	Marketable Equity Securities		Marketable Debt Securities		Total
Mutual funds	$	23,209	$	—	$	23,209
U.S. treasury securities	—		25,798		25,798
Equity securities	50,213		—		50,213
Corporate bonds	—		13,438		13,438
	$	73,422	$	39,236	$	112,658


	December 31, 2021
	Marketable Equity Securities		Marketable Debt Securities		Total
Mutual funds	$	49,662	$	—	$	49,662
Equity securities	36,769		—		36,769
Corporate bonds	—		7,286		7,286
	$	86,431	$	7,286	$	93,717

The amortized costs and fair value of marketable debt securities, by contractual maturity, as of December 31, 2022 (in thousands) are as follows:


	December 31, 2022
	Amortized Cost		Fair Value
Less than 1 year	$	22,014	$	22,196
1 to 5 years	12,086		11,973
More than 5 years	5,036		5,067
Total	$	39,136	$	39,236

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 Consolidated Balance Sheets as of December 31, 2022 and December 31, 2021 (in thousands):

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


	Years Ended December 31,
		2022		2021
Net unrealized losses recognized on marketable equity securities		$	(4,533)	$	(1,669)
Net realized gains (losses) recognized on marketable equity securities		(4,085)		2,148
Net realized gains (losses) recognized on derivative instruments		5,493		(1,467)
Net unrealized gains (losses) recognized on derivative instruments		(662)		103
Net realized gains recognized on marketable debt securities		734		—
Total net gains (losses) recognized in interest and other income (loss), net		$	(3,053)	$	(885)

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 December 31, 2022, and December 31, 2021.

Financial instruments measured at fair value on a recurring basis as of December 31, 2022, and December 31, 2021 are classified based on the valuation technique in the table below (in thousands):


	December 31, 2022
	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:
Certificates of deposit	$	—	$	5,300	$	—	$	5,300
U.S. treasury securities	—		25,798		—		25,798
Mutual funds	23,209		—		—		23,209
Equity securities	50,213		—		—		50,213
Corporate bonds	—		13,438		—		13,438
Total assets at fair value	$	73,422	$	44,536	$	—	$	117,958

Liabilities
Derivative instruments	$	—	$	3,649	$	—	$	3,649
Total liabilities at fair value	$	—	$	3,649	$	—	$	3,649


	December 31, 2021
	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:
Mutual funds	$	49,662	$	—	$	—	49,662
Equity securities	36,769		—		—		36,769
Corporate bonds	—		7,286		—		7,286
Total assets at fair value	$	86,431	$	7,286	$	—	$	93,717

Liabilities
Derivative instruments	$	—	$	6,267	$	—	$	6,267
Total liabilities at fair value	$	—	$	6,267	$	—	$	6,267

If quoted prices for identical instruments are available in an active market, debt securities are classified within Level 1 of the fair value hierarchy. If quoted prices for identical instruments in active markets are not available, fair values are estimated using quoted prices of similar instruments and are classified within Level 2 of the fair value hierarchy. To date, all of our debt securities can be valued using one of these two methodologies.