Fair Value Measurement - Summary of Fair Values and Gross Unrealized Losses of Available for Sale Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, Recorded Basis	$ 44,500	$ 16,364
Less than 12 months, Gross Unrealized Losses	(55)	(82)
12 months or longer, Recorded Basis	226,550	224,185
12 months or longer, Gross Unrealized Losses	(22,382)	(26,566)
Total, Recorded Basis	271,050	240,549
Total, Gross Unrealized Losses	(22,437)	(26,648)
Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, Recorded Basis	6,202	20
Less than 12 months, Gross Unrealized Losses	(17)
12 months or longer, Recorded Basis	60,762	60,065
12 months or longer, Gross Unrealized Losses	(5,441)	(6,409)
Total, Recorded Basis	66,964	60,085
Total, Gross Unrealized Losses	(5,458)	(6,409)
Restricted Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, Recorded Basis	38,298	16,344
Less than 12 months, Gross Unrealized Losses	(38)	(82)
12 months or longer, Recorded Basis	165,788	164,120
12 months or longer, Gross Unrealized Losses	(16,941)	(20,157)
Total, Recorded Basis	204,086	180,464
Total, Gross Unrealized Losses	(16,979)	(20,239)
Corporate Bonds [Member] | Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, Recorded Basis	20	20
12 months or longer, Recorded Basis	25,766	25,377
12 months or longer, Gross Unrealized Losses	(1,950)	(2,365)
Total, Recorded Basis	25,786	25,397
Total, Gross Unrealized Losses	(1,950)	(2,365)
Corporate Bonds [Member] | Restricted Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, Recorded Basis	5,214	11,142
Less than 12 months, Gross Unrealized Losses	(10)	(15)
12 months or longer, Recorded Basis	72,543	71,716
12 months or longer, Gross Unrealized Losses	(6,069)	(7,287)
Total, Recorded Basis	77,757	82,858
Total, Gross Unrealized Losses	(6,079)	(7,302)
U.S. Government Agency Securities [Member] | Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
12 months or longer, Recorded Basis	12,589	12,531
12 months or longer, Gross Unrealized Losses	(121)	(203)
Total, Recorded Basis	12,589	12,531
Total, Gross Unrealized Losses	(121)	(203)
U.S. Government Agency Securities [Member] | Restricted Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
12 months or longer, Recorded Basis	16,037	15,871
12 months or longer, Gross Unrealized Losses	(738)	(914)
Total, Recorded Basis	16,037	15,871
Total, Gross Unrealized Losses	(738)	(914)
U.S. Treasuries [Member] | Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
12 months or longer, Recorded Basis	11,551	11,320
12 months or longer, Gross Unrealized Losses	(911)	(1,140)
Total, Recorded Basis	11,551	11,320
Total, Gross Unrealized Losses	(911)	(1,140)
U.S. Treasuries [Member] | Restricted Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, Recorded Basis	31,959	1,399
Less than 12 months, Gross Unrealized Losses	(14)	(29)
12 months or longer, Recorded Basis	47,726	46,656
12 months or longer, Gross Unrealized Losses	(5,222)	(6,319)
Total, Recorded Basis	79,685	48,055
Total, Gross Unrealized Losses	(5,236)	(6,348)
Mortgage-Backed Securities [Member] | Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
12 months or longer, Recorded Basis	9,551	9,536
12 months or longer, Gross Unrealized Losses	(2,366)	(2,592)
Total, Recorded Basis	9,551	9,536
Total, Gross Unrealized Losses	(2,366)	(2,592)
Mortgage-Backed Securities [Member] | Restricted Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, Recorded Basis	1,080	3,360
Less than 12 months, Gross Unrealized Losses	(14)	(37)
12 months or longer, Recorded Basis	29,482	29,877
12 months or longer, Gross Unrealized Losses	(4,912)	(5,637)
Total, Recorded Basis	30,562	33,237
Total, Gross Unrealized Losses	(4,926)	(5,674)
Asset-Backed Securities [Member] | Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, Recorded Basis	6,182
Less than 12 months, Gross Unrealized Losses	(17)
12 months or longer, Recorded Basis	1,305	1,301
12 months or longer, Gross Unrealized Losses	(93)	(109)
Total, Recorded Basis	7,487	1,301
Total, Gross Unrealized Losses	(110)	(109)
Asset-Backed Securities [Member] | Restricted Investments [Member]
Debt Securities, Available-for-Sale, Unrealized Loss Position [Line Items]
Less than 12 months, Recorded Basis	45	443
Less than 12 months, Gross Unrealized Losses		(1)
Total, Recorded Basis	$ 45	443
Total, Gross Unrealized Losses		$ (1)