Investments - A Summary of the Company's Realized Gains and Losses on Sales, Calls or Redemptions of Investments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Marketable Securities [Line Items]
Proceeds from sales	$ 41,905	$ 50,992	$ 40,579
Gross realized investment gains	6,729	3,715	1,754
Gross realized investment (losses)	(173)	(51)	(21)
Net realized investment gains (losses)	6,556	3,664	1,733
Other, including gains (losses) on calls and redemptions	23	(224)	(38)
Net realized gains (losses) on investments	6,579	3,440	1,695
Fixed Maturity Securities Available for Sale [Member]
Marketable Securities [Line Items]
Proceeds from sales	28,292	42,505	28,191
Gross realized investment gains	181	365	1,751
Gross realized investment (losses)	(173)	(51)	(21)
Net realized investment gains (losses)	8	314	1,730
Other, including gains (losses) on calls and redemptions		(200)	(6)
Net realized gains (losses) on investments	8	(114)	1,724
Equity Securities [Member]
Marketable Securities [Line Items]
Proceeds from sales	12,688	8,487
Gross realized investment gains	6,548	3,350
Net realized investment gains (losses)	6,548	3,350
Net realized gains (losses) on investments	6,548	3,350
Other [Member]
Marketable Securities [Line Items]
Proceeds from sales	925		12,388
Gross realized investment gains			3
Net realized investment gains (losses)			3
Other, including gains (losses) on calls and redemptions	23	24	(32)
Net realized gains (losses) on investments	$ 23	$ 24	$ (29)