Contractual Maturities of Marketable Debt Securities (Detail) - Truck, Parts and Other - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Amortized Cost Maturities:
Within one year	$ 217.5
One to five years	834.5
Six to ten years	23.0
More than ten years	16.0
Amortized Cost	1,091.0	$ 1,154.0
Fair Value Maturities:
Within one year	218.0
One to five years	840.0
Six to ten years	23.0
More than ten years	16.0
Fair Value	$ 1,097.0	$ 1,162.1

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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