Pre-Tax Effects of Derivative Instruments Recognized in OCI (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Derivative [Line Items]
Income before income taxes	$ (429.6)	$ 561.7
Interest-Rate Contracts \| Reclassification out of Accumulated Other Comprehensive Income
Derivative [Line Items]
Income before income taxes	57.9	(33.2)
Foreign-exchange contracts \| Reclassification out of Accumulated Other Comprehensive Income
Derivative [Line Items]
Income before income taxes	(3.1)	1.3
Derivative Contracts \| Reclassification out of Accumulated Other Comprehensive Income
Derivative [Line Items]
Income before income taxes	(54.8)	31.9
Derivative Contracts \| Interest-Rate Contracts
Derivative [Line Items]
Gain (loss) recognized in OCI	(61.7)	31.7
Derivative Contracts \| Foreign-exchange contracts
Derivative [Line Items]
Gain (loss) recognized in OCI	0.3
Truck, Parts and Other
Derivative [Line Items]
Net sales and revenues	4,010.6	4,548.0
Cost of sales and revenues	3,413.6	3,910.2
Interest and other borrowing expenses	0.1	4.5
Income before income taxes	(515.6)	467.6
Truck, Parts and Other \| Derivative Contracts \| Foreign-exchange contracts
Derivative [Line Items]
Gain (loss) recognized in OCI	0.3
Truck, Parts and Other \| Derivative Contracts \| Foreign-exchange contracts \| Reclassification out of Accumulated Other Comprehensive Income
Derivative [Line Items]
Net sales and revenues	0.5
Cost of sales and revenues	(5.3)	3.2
Interest and other borrowing expenses	1.7	(1.9)
Financial Services
Derivative [Line Items]
Interest and other expense, net	30.3	29.1
Income before income taxes	80.3	89.0
Financial Services \| Derivative Contracts \| Interest-Rate Contracts
Derivative [Line Items]
Gain (loss) recognized in OCI	(61.7)	31.7
Financial Services \| Derivative Contracts \| Interest-Rate Contracts \| Reclassification out of Accumulated Other Comprehensive Income
Derivative [Line Items]
Interest and other expense, net	$ 57.9	$ (33.2)

Amount of the cost of borrowed funds accounted for as interest and other borrowing expense.

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- Definition

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(a),(d))
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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+ References

No definition available.

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=51673353&loc=d3e41242-110953

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 10
-Article 5

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Amount before tax and reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
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The net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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