Other Comprehensive Income (Loss) - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments									$ (1,229)	$ 348	$ 5,892
Income taxes, current									(21,526)	4,990	(8,006)
Net of tax	$ 19,999	$ (5,915)	$ 28,566	$ 24,173	$ 25,111	$ (72,275)	$ 7,370	$ 17,537	66,823	(22,257)	20,407
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments									(1,491)	(1,818)	215
Income taxes, current									367	447	(50)
Net of tax									$ (1,124)	$ (1,371)	$ 165