Investments (Tables)

12 Months Ended

Dec. 31, 2023

Gross Unrecognized Gains and Losses and Cost or Amortized Cost, Allowance for Credit Losses, Carrying Amount and Fair Value of Investments Classified as Held-to-Maturity (Detail)

The amortized cost, allowance for credit losses, carrying amount, gross unrecognized gains and losses, and the fair value of those investments classified as held-to-maturity at December 31, 2023 are summarized as follows:

	Amortized Cost		Allowance for Credit Losses			Carrying Amount		Gross Unrecognized Gains		Gross Unrecognized Losses			Fair Value
	(in thousands)
States and political subdivisions	$	416,916	$	(38	)	$	416,878	$	4,166	$	(12,074	)	$	408,970
Corporate bonds		52,321		(142	)		52,179		—		(2,231	)		49,948
U.S. agency-based mortgage-backed    securities		3,297		—			3,297		25		(123	)		3,199
U.S. Treasury securities and obligations    of U.S. government agencies		11,186		—			11,186		26		(273	)		10,939
Asset-backed securities		37		(2	)		35		1		—			36
Totals	$	483,757	$	(182	)	$	483,575	$	4,218	$	(14,701	)	$	473,092

The amortized cost, allowance for credit losses, carrying amount, gross unrealized gains and losses, and the fair value of those investments classified as held-to-maturity at December 31, 2022 are summarized as follows:

	Amortized Cost		Allowance for Credit Losses			Carrying Amount		Gross Unrecognized Gains		Gross Unrecognized Losses			Fair Value
	(in thousands)
States and political subdivisions	$	415,136	$	(40	)	$	415,096	$	922	$	(20,074	)	$	395,944
Corporate bonds		59,903		(196	)		59,707		1		(3,857	)		55,851
U.S. agency-based mortgage-backed    securities		3,696		—			3,696		33		(153	)		3,576
U.S. Treasury securities and obligations    of U.S. government agencies		13,123		—			13,123		25		(442	)		12,706
Asset-backed securities		69		(3	)		66		2		(1	)		67
Totals	$	491,927	$	(239	)	$	491,688	$	983	$	(24,527	)	$	468,144

Gross Unrealized Gains and Losses and Cost or Amortized Cost, Allowance for Credit Losses and Fair Value of Investments Classified as Available-for-sale

The amortized cost, gross unrealized gains and losses, fair value, and the allowance for credit losses of those investments classified as available-for-sale at December 31, 2023 are summarized as follows:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Allowance for Credit Losses
	(in thousands)
States and political subdivisions	$	138,031	$	583	$	(6,719	)	$	131,895	$	—
Corporate bonds		168,134		2,105		(3,486	)		166,753		—
U.S. agency-based mortgage-backed securities		5,190		—		(445	)		4,745		—
U.S. Treasury securities and obligations    of U.S. government agencies		14,816		—		(1,145	)		13,671		—
Totals	$	326,171	$	2,688	$	(11,795	)	$	317,064	$	—

The amortized cost, gross unrealized gains and losses, fair value, and the allowance for credit losses of those investments classified as available-for-sale at December 31, 2022 are summarized as follows:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value		Allowance for Credit Losses
	(in thousands)
States and political subdivisions	$	166,019	$	463	$	(9,826	)	$	156,656	$	—
Corporate bonds		150,915		530		(6,657	)		144,788		—
U.S. agency-based mortgage-backed securities		5,984		—		(538	)		5,446		—
U.S. Treasury securities and obligations    of U.S. government agencies		15,675		9		(1,453	)		14,231		—
Totals	$	338,593	$	1,002	$	(18,474	)	$	321,121	$	—

Gross Unrealized Gains and Losses and Cost of Equity

The cost, gross unrealized gains and losses, and the fair value of equity securities at December 31, 2023 are summarized as follows:

	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(in thousands)
Equity securities:
Domestic common stock	$	44,046	$	13,101	$	—	$	57,147
Total equity securities	$	44,046	$	13,101	$	—	$	57,147

The cost, gross unrealized gains and losses on, and fair value of equity securities at December 31, 2022 are summarized as follows:

	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(in thousands)
Equity securities:
Domestic common stock	$	50,185	$	11,873	$	—	$	62,058
Total equity securities	$	50,185	$	11,873	$	—	$	62,058

A Summary of the Company's Realized Gains and Losses on Sales, Calls or Redemptions of Investments

A summary of the Company’s realized gains and losses on sales, calls or redemptions of investments for 2023, 2022 and 2021 is as follows:

	Fixed Maturity Securities Available-for-Sale			Equity Securities		Other			Total
	(in thousands)
Year ended December 31, 2023
Proceeds from sales	$	28,292		$	12,688	$	925		$	41,905
Gross realized investment gains	$	181		$	6,548	$	—		$	6,729
Gross realized investment losses		(173	)		—		—			(173	)
Net realized investment gains		8			6,548		—			6,556
Other, including gains on calls and redemptions		—			—		23			23
Net realized gains on investments	$	8		$	6,548	$	23		$	6,579
Year ended December 31, 2022
Proceeds from sales	$	42,505		$	8,487	$	—		$	50,992
Gross realized investment gains	$	365		$	3,350	$	—		$	3,715
Gross realized investment losses		(51	)		—		—			(51	)
Net realized investment gains		314			3,350		—			3,664
Other, including losses on calls and redemptions		(200	)		—		(24	)		(224	)
Net realized gains (losses) on investments	$	114		$	3,350	$	(24	)	$	3,440
Year ended December 31, 2021
Proceeds from sales	$	28,191		$	—	$	12,388		$	40,579
Gross realized investment gains	$	1,751		$	—	$	3		$	1,754
Gross realized investment losses		(21	)		—		—			(21	)
Net realized investment gains		1,730			—		3			1,733
Other, including losses on calls and redemptions		(6	)		—		(32	)		(38	)
Net realized gains (losses) on investments	$	1,724		$	—	$	(29	)	$	1,695

Major Categories of the Company's Net Investment Income

Major categories of the Company’s net investment income are summarized as follows:

	Year Ended December 31,
	2023			2022			2021
	(in thousands)
Gross investment income:
Fixed maturity securities	$	26,357		$	24,399		$	24,882
Equity securities		1,456			1,566			1,236
Short-term investments and cash and cash equivalents		4,456			2,260			304
Total gross investment income		32,269			28,225			26,422
Investment expenses		(930	)		(1,002	)		(987	)
Net investment income	$	31,339		$	27,223		$	25,435

Investment Securities Continuous Unrealized Loss Position

The following table summarizes the fair value and gross unrealized losses on fixed maturity securities classified as available-for-sale, aggregated by major investment category and length of time that the individual securities have been in a continuous unrealized loss position:

	Less Than 12 Months				12 Months or Greater				Total
	Fair Value of Investments with Unrealized Losses		Gross Unrealized Losses		Fair Value of Investments with Unrealized Losses		Gross Unrealized Losses		Fair Value of Investments with Unrealized Losses		Gross Unrealized Losses
	(in thousands)
December 31, 2023
Available-for-Sale
States and political subdivisions	$	14,115	$	111	$	72,358	$	6,608	$	86,473	$	6,719
Corporate bonds		26,178		96		93,538		3,390		119,716		3,486
U.S. agency-based mortgage-backed    securities		—		—		4,745		445		4,745		445
U.S. Treasury securities and    obligations of U.S. government    agencies		—		—		13,672		1,145		13,672		1,145
Total available-for-sale securities	$	40,293	$	207	$	184,313	$	11,588	$	224,606	$	11,795
December 31, 2022
Available-for-Sale
States and political subdivisions	$	87,522	$	5,319	$	24,980	$	4,507	$	112,502	$	9,826
Corporate bonds		98,590		4,549		30,011		2,108		128,601		6,657
U.S. agency-based mortgage-backed    securities		4,732		444		714		94		5,446		538
U.S. Treasury securities and    obligations of U.S. government    agencies		5,589		313		7,719		1,140		13,308		1,453
Total available-for-sale securities	$	196,433	$	10,625	$	63,424	$	7,849	$	259,857	$	18,474

Changes in Allowance for Credit Losses by Major Security Type of Investments Classified as Held-to-Maturity

The following table illustrates the changes in the allowance for credit losses by major security type of the investments classified as held-to-maturity for the year ended December 31, 2023.

	States and Political Subdivisions			Corporate Bonds			U.S. Agency -Based Mortgage- Backed Securities		U.S. Treasury Securities and Obligations of U.S. Government Agencies		Asset-Backed Securities			Totals
	(in thousands)
Balance at December 31, 2022	$	40		$	196		$	—	$	—	$	3		$	239
Provision for credit loss benefit		(2	)		(54	)		—		—		(1	)		(57	)
Balance at December 31, 2023	$	38		$	142		$	—	$	—	$	2		$	182

Schedule of Amortized Cost Held-to-Maturity Securities Aggregated By Credit Quality Indicator

The table below presents the amortized cost of held-to-maturity securities aggregated by credit quality indicator as of December 31, 2023.

	States and Political Subdivisions		Corporate Bonds		U.S. Agency -Based Mortgage- Backed Securities		U.S. Treasury Securities and Obligations of U.S. Government Agencies		Asset-Backed Securities		Totals
	Amortized cost
	(in thousands)
AAA/AA/A ratings	$	413,966	$	22,696	$	3,297	$	11,186	$	23	$	451,168
Baa/BBB ratings		2,950		29,625		—		—		14		32,589
B ratings		—		—		—		—		—		—
Total	$	416,916	$	52,321	$	3,297	$	11,186	$	37	$	483,757

Held-to-Maturity Securities [Member]

Summary of Carrying Amount, Amortized Cost and Fair Value of Investments in Fixed Maturity Securities, by Contractual Maturity

A summary of the carrying amounts and fair value of investments in fixed maturity securities classified as held-to-maturity, by contractual maturity, is as follows:

	December 31, 2023				December 31, 2022
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
	(in thousands)
Maturity:
Within one year	$	64,129	$	63,703	$	41,878	$	41,652
After one year through five years		136,854		131,396		165,216		159,006
After five years through ten years		114,990		110,814		121,739		112,665
After ten years		164,270		163,944		159,093		151,178
U.S. agency-based mortgage-backed securities		3,297		3,199		3,696		3,576
Asset-backed securities		35		36		66		67
Totals	$	483,575	$	473,092	$	491,688	$	468,144

Available-for-Sale Securities [Member]

Summary of Carrying Amount, Amortized Cost and Fair Value of Investments in Fixed Maturity Securities, by Contractual Maturity

A summary of the amortized cost and fair value of investments in fixed maturity securities classified as available-for-sale, by contractual maturity, is as follows:

	December 31, 2023				December 31, 2022
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(in thousands)
Maturity:
Within one year	$	25,995	$	25,875	$	28,290	$	27,814
After one year through five years		106,178		102,201		68,876		65,406
After five years through ten years		82,664		80,911		102,296		95,366
After ten years		106,144		103,332		133,147		127,089
U.S. agency-based mortgage-backed securities		5,190		4,745		5,984		5,446
Totals	$	326,171	$	317,064	$	338,593	$	321,121