Equipment on Operating Leases for Truck and Other Segment and for Financial Services Segment (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Subject to or Available for Operating Lease [Line Items]
Total	$ 4,142.0	$ 3,637.8	$ 3,373.0
Truck, Parts and Other
Property Subject to or Available for Operating Lease [Line Items]
Equipment on operating leases	1,615.5	1,282.3
Less allowance for depreciation	(349.8)	(268.4)
Total	1,265.7	1,013.9
Financial Services
Property Subject to or Available for Operating Lease [Line Items]
Equipment on operating leases	4,066.3	3,640.6
Less allowance for depreciation	(1,190.0)	(1,016.7)
Total	$ 2,876.3	$ 2,623.9