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.

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=pcar_CustomerRetailMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsegmentsAxis=pcar_FleetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsegmentsAxis=pcar_OwnerOperatorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=pcar_FinancialServicesMember
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Data Type:	na
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Period Type:

Pre- and Post-Modification Recorded Investment Balances for Finance Receivables Modified by Portfolio Class (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment		$ 1.0		$ 18.0
Post-Modification Recorded Investment		1.0		18.0
Customer Retail \| Fleet
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment		0.9		17.5
Post-Modification Recorded Investment		0.9		17.5
Customer Retail \| Owner/Operator
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment		0.1		0.5
Post-Modification Recorded Investment		$ 0.1		$ 0.5
Financial Services
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment	$ 0.6		$ 8.9
Post-Modification Recorded Investment	0.6		8.9
Financial Services \| Customer Retail \| Fleet
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment	0.5		8.4
Post-Modification Recorded Investment	0.5		8.4
Financial Services \| Customer Retail \| Owner/Operator
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment	0.1		0.5
Post-Modification Recorded Investment	$ 0.1		$ 0.5