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, 2021	Dec. 31, 2020	Dec. 31, 2019
Marketable Securities [Line Items]
Proceeds from sales	$ 40,579	$ 72,395	$ 55,090
Gross realized investment gains	1,754	1,017	176
Gross realized investment (losses)	(21)	(18)	(68)
Net realized investment gains (losses)	1,733	999	108
Other, including gains (losses) on calls and redemptions	(38)	133	(188)
Net realized gains (losses) on investments	1,695	1,132	(80)
Fixed Maturity Securities Available for Sale [Member]
Marketable Securities [Line Items]
Proceeds from sales	28,191	25,436	33,113
Gross realized investment gains	1,751	711	140
Gross realized investment (losses)	(21)	(14)	(68)
Net realized investment gains (losses)	1,730	697	72
Other, including gains (losses) on calls and redemptions	(6)	(43)	(196)
Net realized gains (losses) on investments	1,724	654	(124)
Other [Member]
Marketable Securities [Line Items]
Proceeds from sales	12,388	46,959	21,977
Gross realized investment gains	3	306	36
Gross realized investment (losses)		(4)
Net realized investment gains (losses)	3	302	36
Other, including gains (losses) on calls and redemptions	(32)	176	8
Net realized gains (losses) on investments	$ (29)	$ 478	$ 44