Contractual Maturities of Marketable Debt Securities (Detail) - Truck, Parts and Other - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Amortized Cost Maturities:
Within one year	$ 483.1
One to five years	976.8
Six to ten years	0.2
Amortized Cost	1,460.1	$ 1,445.3
Fair Value Maturities:
Within one year	483.6
One to five years	982.3
Six to ten years	0.2
Fair Value	$ 1,466.1	$ 1,448.1	[1]

[1] The December 31, 2015 consolidated balance sheet has been derived from audited financial statements.