Commitments and Contingent Liabilities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015
Commitments and Contingent Liabilities
Lease period, minimum	5 years
Lease period, maximum	20 years
Loss Contingencies
Letters of credit outstanding	$ 22.9
Surety bonds posted	14.3pag_SuretyBondsPosted
Holdings \| Holdings Bond
Loss Contingencies
Senior unsecured notes issued	700.0
Senior subordinated convertible notes, interest rate (as a percent)	3.80%
Penske Truck Leasing Co., L.P.
Loss Contingencies
Ownership interest in Penske Truck Leasing Co (as a percent)	9.00%
Mitsui and Co
Loss Contingencies
Ownership interest in Penske Truck Leasing Co (as a percent)	20.00%
Purchase of ownership interest	20.00%
Penske Corporation
Loss Contingencies
Ownership interest in Penske Truck Leasing Co (as a percent)	41.10%
GECC
Loss Contingencies
Ownership interest in Penske Truck Leasing Co (as a percent)	29.90%
Guarantee of Indebtedness of Others \| GECC
Loss Contingencies
Percentage of interest agreed to indemnify if GECC required to make any payments of principal or interest	9.00%
Annual fee pay for acting as co-obligor	0.95
Value of interest payments included in maximum amount of Company's potential obligations	$ 63.1

Represents the amount the reporting entity is obliged to pay to co-obligor.

No definition available.

Name:	pag_AnnualFeeForActingAsCoObligor
Namespace Prefix:	pag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lease period , maximum.

+ References

No definition available.

+ Details

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- Definition

Lease period , minimum.

+ References

No definition available.

+ Details

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Namespace Prefix:	pag_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the maximum liability of the reporting entity for required principal payments on the note by third party.

+ References

No definition available.

+ Details

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Namespace Prefix:	pag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the percentage which the reporting entity has agreed to indemnify a third party for payments the third party is required to pay as co-obligor of debt.

+ References

No definition available.

+ Details

Name:	pag_PercentageOfInterestAgreedToIndemnifyToMakeAnyPaymentsOfPrincipalOrInterest
Namespace Prefix:	pag_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of ownership interest purchased in the stock transaction.

+ References

No definition available.

+ Details

Name:	pag_PurchaseOfStockPercentageOfOwnership
Namespace Prefix:	pag_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Surety bonds posted.

+ References

No definition available.

+ Details

Name:	pag_SuretyBondsPosted
Namespace Prefix:	pag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of units or percentage investment held in the subsidiary by the limited liability company or limited partnership.

+ References

No definition available.

+ Details

Name:	us-gaap_SubsidiaryOfLimitedLiabilityCompanyOrLimitedPartnershipOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
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Balance Type:
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- Details

Name:	dei_LegalEntityAxis=pag_MitsuiAndCoMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=pag_PenskeCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=us-gaap_PartnershipInterestMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_GuaranteeOfIndebtednessOfOthersMember
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Data Type:	na
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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=pag_HoldingsMember
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