Balance Sheet Classification of Deferred Tax Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	$ 451.2us-gaap_DeferredTaxAssetsNet	$ 358.1us-gaap_DeferredTaxAssetsNet
Net deferred tax liability	(688.7)us-gaap_DeferredTaxAssetsLiabilitiesNet	(846.5)us-gaap_DeferredTaxAssetsLiabilitiesNet
Truck, Parts and Other \| Other current assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	134.8	122.2
Truck, Parts and Other \| Other Noncurrent Assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	16.0	33.1
Truck, Parts and Other \| Accounts Payable, Accrued Expenses and Other
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	(0.9)	(0.6)
Truck, Parts and Other \| Other liabilities
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	(87.2)	(218.7)
Financial Services \| Other Assets
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets Net	75.0	77.2
Financial Services \| Deferred Taxes And Other Liabilities
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities	$ (826.4)	$ (859.7)

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards, net of deferred tax liability attributable to taxable temporary differences.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b),(c)

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319

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Amount of deferred tax liability attributable to taxable temporary differences net of deferred tax asset attributable to deductible temporary differences and carryforwards after valuation allowances.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32537-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=37586315&loc=d3e31931-109318

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