Contractual Maturities of Marketable Debt Securities (Detail) (Truck, Parts and Other, USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Truck, Parts and Other
Amortized Cost Maturities:
Within one year	$ 486.8
One to five years	759.5
Six to ten years	0.3
Amortized Cost	1,246.6	1,264.9
Fair Value Maturities:
Within one year	487.3
One to five years	762.8
Six to ten years	0.3
Fair Value	$ 1,250.4	$ 1,267.5	[1]

[1] The December 31, 2013 consolidated balance sheet has been derived from audited financial statements.