Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2021 USD ($) Segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Accounting Policies [Abstract]
Reportable segments | Segment	3
Term used to calculate historical weighted average return rate	8 years
Payment to acquire commitment value	$ 1,214,400,000
Deferred revenue	$ 775,200,000	$ 795,800,000
Liquid investments maturity period	90 days
Goodwill	$ 110,600,000	118,800,000
Derivative assets	$ 59,700,000	20,500,000
ASU 2018-14
Accounting Policies [Abstract]
Change in accounting principle, accounting standards update, adopted [true false]	true
Change in accounting principle, accounting standards update adoption date	Jan. 01, 2021
Change in accounting principle, accounting standards update, immaterial effect [true false]	true
ASU 2021-05
Accounting Policies [Abstract]
Change in accounting principle, accounting standards update, adopted [true false]	true
Change in accounting principle, accounting standards update adoption date	Jan. 01, 2021
Change in accounting principle, accounting standards update, immaterial effect [true false]	true
Designated under hedge accounting
Accounting Policies [Abstract]
Derivative assets	$ 58,600,000	19,100,000
Designated under hedge accounting | Interest-Rate Contracts | Other Assets
Accounting Policies [Abstract]
Derivative assets	59,700,000
Trade Receivables
Accounting Policies [Abstract]
Trade and other receivables, net	1,276,400,000	942,700,000
Other Receivables
Accounting Policies [Abstract]
Trade and other receivables, net	298,700,000	254,800,000
Financial Services
Accounting Policies [Abstract]
Total operating lease revenue	831,600,000	802,300,000	$ 798,200,000
Financing receivable, recorded investment, 90 days past due and still accruing	$ 0	$ 0
Months contractual terms extended	8 months	3 months
Financial Services | Designated under hedge accounting | Interest-Rate Contracts | Other Assets
Accounting Policies [Abstract]
Derivative assets	$ 30,800,000	$ 16,400,000
Financial Services | Operating Lease
Accounting Policies [Abstract]
Total operating lease revenue	831,600,000	802,300,000	798,200,000
Depreciation and other expenses	665,700,000	776,500,000	$ 721,600,000
Truck, Parts and Other
Accounting Policies [Abstract]
Trade and other receivables, net	$ 1,575,100,000	$ 1,197,500,000
Trade receivable days outstanding considered past due	30 days	30 days	30 days
Allowance for credit losses for Truck, Parts and Other	$ 600,000	$ 600,000
Net charge-offs	$ 0	0	$ 300,000
Engines manufactured by PACCAR
Accounting Policies [Abstract]
Warranty period	2 years
Trucks | Truck Sales
Accounting Policies [Abstract]
Total operating lease revenue	$ 113,800,000	$ 104,200,000	$ 159,700,000
Maximum
Accounting Policies [Abstract]
Warranty period	5 years
Lease and guarantee periods (in years)	5 years
Estimated useful lives of equipment	10 years
Maximum | Financial Services
Accounting Policies [Abstract]
Operating lease term	5 years
Maximum | Financial Services | Loans and Leases
Accounting Policies [Abstract]
Contractual terms of retails loans and finance leases	5 years
Maximum | Trucks | Financial Services
Accounting Policies [Abstract]
Finance leases, lease term	5 years
Minimum
Accounting Policies [Abstract]
Warranty period	1 year
Lease and guarantee periods (in years)	3 years
Estimated useful lives of equipment	3 years
Minimum | Financial Services
Accounting Policies [Abstract]
Operating lease term	3 years
Minimum | Financial Services | Loans and Leases
Accounting Policies [Abstract]
Contractual terms of retails loans and finance leases	3 years
Minimum | Trucks | Financial Services
Accounting Policies [Abstract]
Finance leases, lease term	3 years