Significant Accounting Policies - Additional Information (Detail) shares in Millions			12 Months Ended
	Dec. 06, 2022	Jan. 01, 2020 USD ($)	Dec. 31, 2022 USD ($) Segment shares	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($)	Jan. 17, 2023 shares	Mar. 31, 2022
Accounting Policies [Abstract]
Reportable segments | Segment			3
Term used to calculate historical weighted average return rate			9 years
Payment to acquire commitment value			$ 971,900,000
Deferred revenue			$ 904,900,000	$ 775,200,000
Liquid investments maturity period			90 days
Goodwill			$ 104,100,000	110,600,000
Derivative assets			$ 119,400,000	$ 59,700,000
Dividends payable, date declared	Dec. 06, 2022
Dividends payable, date to be paid	Feb. 07, 2023
Common stock dividend payable	50.00%
Common stock, issued | shares			522.0	347.3
Restatement effect on percentage dividend	50.00%
Percentage of inventories valued using LIFO method of accounting							41.00%
Retained earnings			$ 13,402,400,000	$ 12,025,800,000
ASU 2021-10
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, 2022
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, 2022
Change in accounting principle, accounting standards update, immaterial effect [true false]			true
Cumulative Effect, Period of Adoption, Adjustment | Adjustment
Accounting Policies [Abstract]
Retained earnings		$ 10,539,000,000.0
Increase (decrease) in retained earnings accumulated deficit		$ 140,500,000
Subsequent Event
Accounting Policies [Abstract]
Common stock, issued | shares						174,035,361.0
Fractional shares paid in cash | shares						411.0
Designated under hedge accounting
Accounting Policies [Abstract]
Derivative assets			$ 118,400,000	58,600,000
Designated under hedge accounting | Interest-Rate Contracts | Other Assets
Accounting Policies [Abstract]
Derivative assets			119,400,000
Trade Receivables
Accounting Policies [Abstract]
Trade and other receivables, net			1,600,100,000	1,276,400,000
Other Receivables
Accounting Policies [Abstract]
Trade and other receivables, net			319,700,000	298,700,000
Financial Services
Accounting Policies [Abstract]
Total operating lease revenue			788,800,000	831,600,000	$ 802,300,000
Financing receivable, recorded investment, 90 days past due and still accruing			$ 0	$ 0
Months contractual terms extended			3 months	8 months
Financial Services | Designated under hedge accounting | Interest-Rate Contracts | Other Assets
Accounting Policies [Abstract]
Derivative assets			$ 58,000,000.0	$ 30,800,000
Financial Services | Operating Lease
Accounting Policies [Abstract]
Total operating lease revenue			$ 788,800,000	$ 831,600,000	$ 802,300,000
Operating Lease, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration]			Investment income	Investment income	Investment income
Depreciation and other expenses			$ 490,000,000.0	$ 665,700,000	$ 776,500,000
Truck, Parts and Other
Accounting Policies [Abstract]
Trade and other receivables, net			$ 1,919,800,000	$ 1,575,100,000
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			2,000,000	0	$ 0
Retained earnings			13,402,400,000	12,025,800,000
Truck, Parts and Other | Adjustment
Accounting Policies [Abstract]
Retained earnings			$ 193,800,000	156,600,000
Engines manufactured by PACCAR
Accounting Policies [Abstract]
Warranty period			2 years
Trucks | Truck Sales
Accounting Policies [Abstract]
Total operating lease revenue			$ 105,900,000	$ 113,800,000	$ 104,200,000
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