Investments in Marketable Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Net unrealized gains (losses) on marketable equity securities recognized in investment income	$ 1,900,000	$ 3,200,000	$ (5,200,000)
Allowance for credit losses	0	0
Truck, Parts and Other
Schedule Of Available For Sale Securities [Line Items]
Gross realized gains from sales of marketable debt securities	2,100,000	900,000	500,000
Gross realized loss from sales of marketable debt securities	$ 4,500,000	$ 4,500,000	$ 2,300,000