Significant Accounting Policies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) Segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Accounting Policies [Abstract]
Reportable segments | Segment	3
Liquid investments maturity period	90 days
Goodwill	$ 105.6	$ 128.6
Goodwill, impairment charges	0.0	0.0	$ 0.0
Derivative assets	137.3	89.2
Trade Receivables
Accounting Policies [Abstract]
Trade and other receivables, net	739.2	882.2
Other Receivables
Accounting Policies [Abstract]
Trade and other receivables, net	$ 139.8	165.0
Engines manufactured by PACCAR
Accounting Policies [Abstract]
Warranty period	2 years
Designated as Hedging Instrument
Accounting Policies [Abstract]
Derivative assets	$ 136.1	83.9
Minimum
Accounting Policies [Abstract]
Lease and guarantee periods (in years)	3 years
Warranty period	1 year
Maximum
Accounting Policies [Abstract]
Lease and guarantee periods (in years)	5 years
Warranty period	5 years
Equipment on Operating Lease | Minimum
Accounting Policies [Abstract]
Estimated useful life of equipment (in years)	4 years
Equipment on Operating Lease | Maximum
Accounting Policies [Abstract]
Estimated useful life of equipment (in years)	9 years
Truck, Parts and Other
Accounting Policies [Abstract]
Trade and other receivables, net	$ 879.0	$ 1,047.1
Trade receivable days outstanding considered past due	30 days	30 days	30 days
Allowance for credit losses for Truck, Parts and Other	$ 1.3	$ 1.9
Net charge-offs	0.3	0.2	$ 0.2
Financial Services
Accounting Policies [Abstract]
Lease rental revenue	728.5	741.6	712.1
Depreciation and other expenses	$ 583.7	$ 588.5	571.7
Months contractual terms extended	7 months	5 months
Financial Services | Designated as Hedging Instrument | Interest-Rate Contracts | Other Assets
Accounting Policies [Abstract]
Derivative assets	$ 132.2	$ 82.7
Financial Services | Minimum | Loans And Leases
Accounting Policies [Abstract]
Receivable, collection period	36 months
Financial Services | Minimum | Loans Receivable
Accounting Policies [Abstract]
Origination cost, amortization period	36 months
Financial Services | Maximum | Loans And Leases
Accounting Policies [Abstract]
Receivable, collection period	60 months
Financial Services | Maximum | Loans Receivable
Accounting Policies [Abstract]
Origination cost, amortization period	60 months
Financial Services | Operating Lease
Accounting Policies [Abstract]
Lease rental revenue	$ 668.6	681.5	631.7
Depreciation and other expenses	$ 536.2	$ 544.0	$ 503.5