Comprehensive Income and Accumulated Other Comprehensive Income (Loss) - Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized gains on investments	$ 75	$ 1,079	$ 333	$ 1,817
Income before income taxes	19,568	7,123	41,103	28,545
Income tax expense	(3,941)	(991)	(8,137)	(5,082)
Net income	15,627	6,132	32,966	23,463
Unrealized Gains (Losses) On Debt Securities, Net Of Tax [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net realized gains on investments	(189)	865	(195)	894
Income before income taxes	(189)	865	(195)	894
Income tax expense	40	(182)	41	(188)
Net income	$ (149)	$ 683	$ (154)	$ 706