v3.26.1
Schedule of Assets - Schedule of Assets Held at End of Year (Details) - EBP 002
12 Months Ended
Dec. 31, 2025
USD ($)
shares
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Plan Name Savings Investment Plan
Entity Tax Identification Number 91-0351110
EBP, Plan Number 002
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 2,975,548,042
Participant loans $ 65,128,740
Investment, Identifier [Axis]: Commingled Trust Funds, BlackRock, International  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Commingled Trust Funds
EBP, Investment, Issuer Name [Extensible Enumeration] International [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 397,720
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 9,571,173
Investment, Identifier [Axis]: Commingled Trust Funds, Fidelity Management Trust Company, Contrafund Pool Class D  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Commingled Trust Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Contrafund Pool Class D [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 7,486,562
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 417,151,227
Investment, Identifier [Axis]: Commingled Trust Funds, Fidelity Management Trust Company, Managed Income Portfolio II Class 3  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Commingled Trust Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Managed Income Portfolio II Class 3 [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 127,265,556
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 127,265,556
Investment, Identifier [Axis]: Commingled Trust Funds, Northern Trust Funds, Aggregate Bond Index Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Commingled Trust Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Aggregate Bond Index Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 159,705
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 21,456,322
Investment, Identifier [Axis]: Commingled Trust Funds, Northern Trust Funds, Collective Russell 2000 Index  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Commingled Trust Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Collective Russell 2000 Index [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 57,665
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 23,929,618
Investment, Identifier [Axis]: Commingled Trust Funds, Northern Trust Funds, EAFE Index Fund Tier 3  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Commingled Trust Funds
EBP, Investment, Issuer Name [Extensible Enumeration] EAFE Index Fund Tier 3 [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 196,768
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 40,148,567
Investment, Identifier [Axis]: Commingled Trust Funds, Northern Trust Funds, S&P 500 Index Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Commingled Trust Funds
EBP, Investment, Issuer Name [Extensible Enumeration] S&P 500 Index Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 417,858
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 288,936,587
Investment, Identifier [Axis]: Money Market Fund, Fidelity Management Trust Company, Fidelity Government Money Market  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Money Market Funds [Member]
EBP, Investment, Issuer Name [Extensible Enumeration] Fidelity Government Money Market [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 143,004
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 143,004
Investment, Identifier [Axis]: Mutual funds, Fidelity Management Trust Company, Freedom Index 2010 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Freedom Index 2010 Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 439,785
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 5,941,491
Investment, Identifier [Axis]: Mutual funds, Fidelity Management Trust Company, Freedom Index 2020 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Freedom Index 2020 Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 2,667,339
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 44,971,332
Investment, Identifier [Axis]: Mutual funds, Fidelity Management Trust Company, Freedom Index 2030 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Freedom Index 2030 Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 8,264,440
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 186,858,992
Investment, Identifier [Axis]: Mutual funds, Fidelity Management Trust Company, Freedom Index 2040 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Freedom Index 2040 Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 6,189,895
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 178,454,667
Investment, Identifier [Axis]: Mutual funds, Fidelity Management Trust Company, Freedom Index 2050 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Freedom Index 2050 Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 4,302,782
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 132,998,994
Investment, Identifier [Axis]: Mutual funds, Fidelity Management Trust Company, Freedom Index 2060 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Freedom Index 2060 Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 3,303,348
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 71,253,225
Investment, Identifier [Axis]: Mutual funds, Fidelity Management Trust Company, Freedom Index 2070 Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Freedom Index 2070 Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 105,211
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 1,298,310
Investment, Identifier [Axis]: Mutual funds, Fidelity Management Trust Company, Freedom Index Retirement Fund  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Freedom Index Income Fund [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 665,514
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 8,219,095
Investment, Identifier [Axis]: Mutual funds, JP Morgan Mid Cap Value Fund, Institutional Class  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Institutional Class [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 1,821,258
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 58,118,174
Investment, Identifier [Axis]: Mutual funds, PIMCO Total Return Fund, Institutional Class  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Investment, Current Value, Type [Extensible Enumeration] Mutual Funds
EBP, Investment, Issuer Name [Extensible Enumeration] Institutional Class [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 3,501,682
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 31,024,906
Investment, Identifier [Axis]: PACCAR Inc Common Stock  
EBP, Schedule of Asset Held for Investment [Line Items]  
EBP, Asset Held for Investment, Party-in-Interest [true false] true
EBP, Investment, Current Value, Type [Extensible Enumeration] EBP, Employer, Common Stock [Member]
EBP, Investment, Issuer Name [Extensible Enumeration] PACCAR Inc Common Stock [Member]
EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] us-gaap-ebp:EmployeeBenefitPlanParticipantDirectedMember
Employee Benefit Plan, Investment, number of shares / units | shares 12,124,816
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 1,327,806,802
Minimum  
EBP, Schedule of Asset Held for Investment [Line Items]  
Employee benefit plan, asset held for investment, participant loan, interest rate 4.25%
Maximum  
EBP, Schedule of Asset Held for Investment [Line Items]  
Employee benefit plan, asset held for investment, participant loan, maturity year 2040
Employee benefit plan, asset held for investment, participant loan, interest rate 9.50%
Commingled Trust Funds  
EBP, Schedule of Asset Held for Investment [Line Items]  
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 928,459,050
Mutual Funds  
EBP, Schedule of Asset Held for Investment [Line Items]  
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value $ 719,139,186