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, 2022	Dec. 31, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Proceeds from sales	$ 50,992	$ 40,579	$ 72,395
Gross realized investment gains	3,715	1,754	1,017
Gross realized investment (losses)	(51)	(21)	(18)
Net realized investment gains (losses)	3,664	1,733	999
Other, including gains (losses) on calls and redemptions	(224)	(38)	133
Net realized gains (losses) on investments	3,440	1,695	1,132
Fixed Maturity Securities Available for Sale [Member]
Marketable Securities [Line Items]
Proceeds from sales	42,505	28,191	25,436
Gross realized investment gains	365	1,751	711
Gross realized investment (losses)	(51)	(21)	(14)
Net realized investment gains (losses)	314	1,730	697
Other, including gains (losses) on calls and redemptions	(200)	(6)	(43)
Net realized gains (losses) on investments	114	1,724	654
Equity Securities [Member]
Marketable Securities [Line Items]
Proceeds from sales	8,487
Gross realized investment gains	3,350
Net realized investment gains (losses)	3,350
Net realized gains (losses) on investments	3,350
Other [Member]
Marketable Securities [Line Items]
Proceeds from sales		12,388	46,959
Gross realized investment gains		3	306
Gross realized investment (losses)			(4)
Net realized investment gains (losses)		3	302
Other, including gains (losses) on calls and redemptions	(24)	(32)	176
Net realized gains (losses) on investments	$ (24)	$ (29)	$ 478