Marketable Securities

3 Months Ended

Mar. 31, 2024

3. Marketable Securities

The following tables summarize the Company's marketable securities accounted for as available-for-sale securities (in thousands, except years):


	March 31, 2024
	Maturity (in years)	Amortized cost		Unrealized gains		Unrealized losses			Estimated fair value
U.S. Treasury securities	1 or less	$	63,024	$	33	$	—		$	63,057
U.S. government agency securities	1 or less		36,588		16		(23	)		36,581
U.S. Treasury securities	1-2		21,998		17		(53	)		21,962
U.S. government agency securities	1-2		6,492		4		—			6,496
Total		$	128,102	$	70	$	(76	)	$	128,096


	December 31, 2023
	Maturity (in years)	Amortized cost		Unrealized gains		Unrealized losses			Estimated fair value
U.S. Treasury securities	1 or less	$	76,481	$	153	$	—		$	76,634
U.S. government agency securities	1 or less		37,376		38		(3	)		37,411
U.S. Treasury securities	1-2		18,846		118		—			18,964
U.S. government agency securities	1-2		12,379		75		—			12,454
Total		$	145,082	$	384	$	(3	)	$	145,463

The following tables present fair values and gross unrealized losses for those available-for-sale securities that were in an unrealized loss position, aggregated by category and the length of time that the securities have been in a continuous loss position (in thousands):


	March 31, 2024
	Unrealized losses less than 12 months					Unrealized losses 12 months or greater				Total
	Fair value		Unrealized losses			Fair value		Unrealized losses		Fair value		Unrealized losses
U.S. Treasury securities	$	12,204	$	(53	)	$	—	$	—	$	12,204	$	(53	)
U.S. government agency securities	$	16,805	$	(23	)	$	—	$	—	$	16,805	$	(23	)
Total	$	29,009	$	(76	)	$	—	$	—	$	29,009	$	(76	)


	December 31, 2023
	Unrealized losses less than 12 months					Unrealized losses 12 months or greater				Total
	Fair value		Unrealized losses			Fair value		Unrealized losses		Fair value		Unrealized losses
U.S. government agency securities	$	9,939	$	(3	)	$	—	$	—	$	9,939	$	(3	)
Total	$	9,939	$	(3	)	$	—	$	—	$	9,939	$	(3	)

As of March 31, 2024, there were six available-for-sale securities with an estimated fair value of $29.0 million in a gross unrealized loss position for less than 12 months. As of March 31, 2024, unrealized losses on available-for-sale securities are not attributed to credit risk. The Company believes that an allowance for credit losses is unnecessary because the unrealized loss is due to market factors and interest rate fluctuations. Additionally, the Company does not intend to sell the securities nor is it more likely than not that the Company will be required to sell the securities before recovery of their amortized cost basis.

Accrued interest on the Company's available-for-sale securities was $1.5 million as of March 31, 2024 and is included in prepaid and other current assets on the condensed balance sheet.