Contractual Maturities of Marketable Debt Securities (Detail) - Truck, Parts and Other - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Amortized Cost Maturities:
Within one year	$ 295.8
One to five years	770.7
Six to ten years	13.2
More than ten years	29.2
Amortized Cost	1,108.9	$ 1,023.5
Fair Value Maturities:
Within one year	296.2
One to five years	778.7
Six to ten years	13.2
More than ten years	29.2
Fair Value	$ 1,117.3	$ 1,020.4	[1]

[1] The December 31, 2018 consolidated balance sheet has been derived from audited financial statements.