Schedule of Assets - Schedule of Assets Held at End of Year (Details) - EBP 002	12 Months Ended
Dec. 31, 2024 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	$ 2,792,943,297
Participant loans	$ 63,384,614
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	178,090
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 3,506,469
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	8,547,800
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 389,010,394
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	121,077,175
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 121,077,175
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	138,615
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 17,362,957
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	62,001
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 22,802,268
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	190,521
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 29,490,803
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	436,477
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 256,080,879
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	563,134
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 563,134
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	319,179
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 4,095,063
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	3,184,005
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 50,211,763
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	8,163,191
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 164,651,557
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	5,981,550
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 147,265,760
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	3,896,323
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 101,187,499
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	2,983,724
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 54,035,248
Investment, Identifier [Axis]: Mutual funds, Fidelity Management Trust Company, Freedom Index Income 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	636,376
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 7,445,594
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	1,707,097
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 62,723,278
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	3,545,838
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 30,068,706
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	12,798,975
Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value	$ 1,331,364,750
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	2039
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	$ 839,330,945
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	$ 621,684,468

The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

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Employee benefit plan participant loan maturity year.

+ References

No definition available.

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- Definition

Name of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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- Definition

Current value of investment, excluding plan interest in master trust, in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract.

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- Definition

Indicates status of participation by participant for investment, excluding plan interest in master trust, in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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- Definition

Amount, after deemed distribution, of participant loan in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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- Definition

Indicates (true false) whether asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) was transacted with party-in-interest.

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- Definition

Indicates name of issuer of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

Number of shares or units of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Indicates type of investment at current value held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

Interest rate on participant loan in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

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- Definition

Plan number of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), in three-digit numeric format.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
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-Number 2520
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