Contractual Maturities of Marketable Debt Securities (Detail) - Truck, Parts and Other $ in Millions	Jun. 30, 2021 USD ($)
Amortized Cost Maturities:
Within one year	$ 408.9
One to five years	991.0
Six to ten years	13.9
More than ten years	4.9
Marketable debt securities, Cost	1,418.7
Fair Value Maturities:
Within one year	411.0
One to five years	999.5
Six to ten years	13.9
More than ten years	4.9
Fair Value	$ 1,429.3

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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