Reclassifications Out of Accumulated Other Comprehensive Income (Parenthetical) (Detail) (Truck, Parts and Other, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pension plans, Actuarial loss, pre- tax	$ 20.1	$ 41.7
Pension plans, Prior service costs, pre-tax	1.2	1.3
Cost of sales and revenues
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pension plans, Actuarial loss, pre- tax	11.1	21.4
Pension plans, Prior service costs, pre-tax	1.0	0.4
SG&A
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pension plans, Actuarial loss, pre- tax	9.0	20.3
Pension plans, Prior service costs, pre-tax	0.2	0.6
R&D
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pension plans, Prior service costs, pre-tax		$ 0.3