Contractual Maturities of Marketable Debt Securities (Detail) (Truck, Parts and Other, USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Truck, Parts and Other
Amortized Cost Maturities:
Within one year	$ 448.0
One to five years	880.3
More than ten years	0.4
Amortized Cost	1,328.7	1,264.9
Fair Value Maturities:
Within one year	448.5
One to five years	886.1
More than ten years	0.4
Fair Value	$ 1,335.0	$ 1,267.5	[1]

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