The following tables present amortized cost and fair values of investments at March 31, 2024 and December 31, 2023, respectively:


March 31, 2024	Amortized cost		Accumulated unrealized gains		Accumulated unrealized losses		Fair value
	(in thousands)
Investment securities, held-to-maturity
U.S. government and government agencies and authorities	$	7,715	$	—	$	(169)	$	7,546
Investment securities, available-for-sale
U.S. government and government agencies and authorities	137,911		235		(2,782)		135,364
Corporate debt securities	77,957		91		(104)		77,944
Other	1,881		—		—		1,881
Total held-to-maturity and available-for-sale investment securities	$	225,464	$	326	$	(3,055)	$	222,735


December 31, 2023	Amortized cost		Accumulated unrealized gains		Accumulated unrealized losses		Fair value
	(in thousands)
Investment securities, held-to-maturity
U.S. government and government agencies and authorities	$	7,695	$	—	$	(225)	$	7,470
Investment securities, available-for-sale
U.S. government and government agencies and authorities	126,071		713		(3,070)		123,714
Corporate debt	95,354		165		(176)		95,343
Other	1,855		—		(2)		1,853
Total held-to-maturity and available-for-sale investment securities	$	230,975	$	878	$	(3,473)	$	228,380

The following table presents the amortized cost and fair value of debt securities at March 31, 2024, by contractual maturity:


March 31, 2024	Held-to-maturity				Available-for-sale
	Amortized cost		Fair value		Amortized cost		Fair value
	(in thousands)
Due within one year	$	6,923	$	6,853	$	119,528	$	118,056
Due after one year through five years	680		602		98,221		97,133
Due after five years through ten years	—		—		—		—
Due after ten years	112		91		—		—
Total	$	7,715	$	7,546	$	217,749	$	215,189

For the three months ended March 31, 2024 and 2023, respectively, net investment income, which is included within Other income within the Condensed Consolidated Statements of Operations and Comprehensive Loss, was derived from the following sources:


	Three Months Ended March 31,
	2024		2023
	(in thousands)
Cash and cash equivalents	$	2,186	$	1,629
Short-term investments	174		492
Investment securities	2,108		1,814
Investment income, net	$	4,468	$	3,935

Gross unrealized losses and fair values aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position were as follows at March 31, 2024, and December 31, 2023, respectively:


March 31, 2024	Less than 12 months				Greater than 12 months				Total
	Fair value		Unrealized loss		Fair value		Unrealized loss		Fair value		Unrealized loss
	(in thousands, except number of positions)
U.S. government and government agencies and authorities	$	33,908	$	(54)	$	61,799	$	(2,906)	$	95,707	$	(2,960)
Corporate debt securities	38,850		(75)		6,691		(20)		45,541		(95)
Total	$	72,758	$	(129)	$	68,490	$	(2,926)	$	141,248	$	(3,055)
Number of positions	55				29				84


December 31, 2023	Less than 12 months				Greater than 12 months				Total
	Fair value		Unrealized loss		Fair value		Unrealized loss		Fair value		Unrealized loss
	(in thousands, except number of positions)
U.S. government and government agencies and authorities	$	12,584	$	(32)	$	61,628	$	(3,259)	$	74,212	$	(3,291)
Corporate debt securities	61,007		(175)		5,017		(7)		66,024		(182)
Total	$	73,591	$	(207)	$	66,645	$	(3,266)	$	140,236	$	(3,473)
Number of positions	69				27				96

The Company did not record any credit allowances for debt securities that were in an unrealized loss position at March 31, 2024 and December 31, 2023.

At March 31, 2024, all securities were investment grade, with credit ratings of BBB+ or higher by S&P Global or as determined by other credit rating agencies within the Company's investment policy. Unrealized losses on investment grade securities are principally related to changes in interest rates or changes in issuer or sector related credit spreads since the securities were acquired. The gross unrealized investment losses at March 31, 2024, were assessed, based on, among other things:

•The relative magnitude to which fair values of these securities have been below their amortized cost was not indicative of an impairment loss;

•The absence of compelling evidence that would cause the Company to call into question the financial condition or near-term prospects of the issuer of the applicable security; and

•The Company's ability and intent to hold the applicable security for a period of time sufficient to allow for any anticipated recovery.

Proceeds from sales and maturities of investment securities, inclusive of short-term investments, and related gross realized gains (losses) which are included within Other income within the Condensed Consolidated Statements of Operations and Comprehensive Loss, were as follows for the three months ended March 31, 2024 and 2023, respectively:


	Three Months Ended March 31,
	2024		2023
	(in thousands)
Proceeds from sales of investment securities	$	—	$	15,001
Proceeds from maturities of investment securities	33,735		63,324

Gross realized gains	—		—
Gross realized losses	—		—
Net realized gains (losses)	$	—	$	—

At March 31, 2024 and December 31, 2023, the Company had $14.8 million and $14.7 million, respectively, in deposits with various states and regulatory bodies that are included as part of the Company's investment balances.