Contractual Maturities of Marketable Debt Securities (Detail) - Truck, Parts and Other $ in Millions	Dec. 31, 2023 USD ($)
Amortized Cost Maturities:
Within one year	$ 488.3
One to five years	1,336.0
Six to ten years	0.7
More than ten years	11.9
Marketable debt securities, Cost	1,836.9
Fair Value Maturities:
Within one year	482.5
One to five years	1,324.5
Six to ten years	0.6
More than ten years	10.6
Fair Value	$ 1,818.2

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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