The carrying amounts of cash and cash equivalents, restricted cash, accounts payable, and accrued expenses approximated their estimated fair values due to the short-term nature of these financial instruments. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value are performed in a manner to maximize the use of observable inputs and minimize the use of unobservable inputs. The accounting standard describes a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value, which are the following:

Level 1— Quoted prices (unadjusted) in active markets that are accessible at the market date for identical unrestricted assets or liabilities.

Level 2— Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs for which all significant inputs are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3— Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The table below presents information about the Company’s assets and liabilities that are regularly measured and carried at fair value and indicate the level within the fair value hierarchy of valuation techniques the Company utilized to determine such fair values (in thousands):


	Fair Value Measurements Using
			Quoted
			Prices		Significant
			(unadjusted)		Other		Significant
	Total		in Active		Observable		Unobservable
	Carrying		Markets		Inputs		Inputs
	Value		(Level 1)		(Level 2)		(Level 3)
	(In thousands)
March 31, 2024
Assets:
Cash and cash equivalents	$	114,615	$	94,707	$	19,908	$	—
Short-term investments		319,963		—		319,963		—
Long-term investments		87,416		—		87,416		—
Total assets	$	521,994	$	94,707	$	427,287	$	—
December 31, 2023
Assets:
Cash and cash equivalents	$	295,394	$	295,394	$	—	$	—
Short-term investments		275,304		—		275,304		—
Long-term investments		29,829		—		29,829		—
Total assets	$	600,527	$	295,394	$	305,133	$	—

There have been no material impairments of our assets measured and carried at fair value during the period ended March 31, 2024 and 2023. In addition, there have been no changes in valuation techniques during the periods ended March 31, 2024 and 2023. The fair value of Level 1 instruments classified as cash equivalents are valued using quoted market prices in active markets. The fair value of Level 2 instruments classified as cash equivalents and short and long-term investments are determined based on quoted prices in active markets, which are either directly or indirectly observable as of the reporting date with fair value being determined using models or other valuation methodologies.

The Company’s short and long-term investments are classified as available-for-sale securities. As of March 31, 2024, the remaining contractual maturities of the available-for-sale securities were 1 to 19 months, and the balance in the Company’s accumulated other comprehensive loss was comprised solely of activity related to the Company’s available-for-sale securities. There were no realized gains or losses recognized on the sale or maturity of available-for-sale securities, during the three months ended March 31, 2024 and 2023. As a result, the Company did not reclassify any amounts out of accumulated other comprehensive loss for the same periods. The Company has a limited number of available-for-sale securities that are not in significant loss positions as of March 31, 2024, which the Company does not intend to sell, and it has concluded it will not be required to sell before recovery of the amortized cost for the investment at maturity.

The following table summarizes the available-for-sale securities:


	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses			Fair Value
	(In thousands)
March 31, 2024
Commercial paper	$	180,927	$	—	$	(101	)	$	180,826
Corporate bonds		47,604		—		(72	)		47,532
US Treasury		176,012		—		(548	)		175,464
Federal bonds		23,500		—		(35	)		23,465
	$	428,043	$	—	$	(756	)	$	427,287
December 31, 2023
Commercial paper	$	160,657	$	149	$	—		$	160,806
Corporate bonds		47,150		62		—			47,212
US Treasury		68,111		46		—			68,157
Federal bonds		28,998		—		(40	)		28,958
	$	304,916	$	257	$	(40	)	$	305,133