The percentage of investment ownership.

No definition available.

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

- Definition

Represents the minimum number of vehicle brands offered.

+ References

No definition available.

+ Details

Name:	pag_MinimumNumberOfBrandedVehiclesOffered
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the minimum number of dealership locations wherein the vehicles were distributed and sold.

+ References

No definition available.

+ Details

Name:	pag_MinimumNumberOfDealershipLocations
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the minimum number of vehicles retailed and wholesaled.

+ References

No definition available.

+ Details

Name:	pag_MinimumNumberOfVehiclesRetailedAndWholesaled
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of franchises acquired.

+ References

No definition available.

+ Details

Name:	pag_NumberOfFranchisesAcquired
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of full service retail locations acquired.

+ References

No definition available.

+ Details

Name:	pag_NumberOfFullServiceRetailLocationsAcquired
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of full service retail locations operated by the equity method investee.

+ References

No definition available.

+ Details

Name:	pag_NumberOfFullServiceRetailLocationsOperated
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of operating franchises.

+ References

No definition available.

+ Details

Name:	pag_NumberOfOperatingFranchises
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Total number of owned and operated franchises.

+ References

No definition available.

+ Details

Name:	pag_NumberOfOwnedAndOperatedFranchises
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of owned and operated franchises in domestic country.

+ References

No definition available.

+ Details

Name:	pag_NumberOfOwnedAndOperatedFranchisesInDomesticCountry
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of owned and operated franchises in foreign countries.

+ References

No definition available.

+ Details

Name:	pag_NumberOfOwnedAndOperatedFranchisesInForeignCountries
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of retail commercial vehicle dealerships owned by the reporting entity.

+ References

No definition available.

+ Details

Name:	pag_NumberOfRetailCommercialVehicleDealershipsOwnedByReportingEntity
Namespace Prefix:	pag_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13537-108611

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13531-108611

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 18

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592

+ Details

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

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

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

- Details

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

- Definition

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

+ Details

Name:	us-gaap_SalesRevenueNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=pag_AutomotiveRetailFranchisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=pag_RetailCommercialTruckDealershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=pag_WesternStarTrucksAustraliaMember
Namespace Prefix:
Data Type:	na
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- Details

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Interim Financial Statements (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended	0 Months Ended
	Mar. 31, 2015 item	Mar. 31, 2014	Dec. 31, 2014	Mar. 31, 2015 item	Nov. 30, 2014	Sep. 30, 2014
Interim Financial Statements.
Total revenues	$ 4,471.1us-gaap_SalesRevenueNet	$ 4,015.2us-gaap_SalesRevenueNet	$ 16,600.0us-gaap_SalesRevenueNet
Total number of owned and operated franchises	328pag_NumberOfOwnedAndOperatedFranchises			328pag_NumberOfOwnedAndOperatedFranchises
Number of owned and operated franchises in US	180			180
Number of owned and operated franchises outside US	148			148
Minimum number of vehicles retailed and wholesaled	122,000
Interim Financial Statements
Minimum number of vehicle brands offered	40
Commercial Vehicle Distribution
Interim Financial Statements
Minimum number of dealership locations				70
Number of commercial vehicle dealerships				3
Retail Automotive Franchise
Interim Financial Statements
Number of acquired franchises	1	1
Retail Commercial Truck Dealership
Interim Financial Statements
Number of acquired franchises	2
Number of operating locations	16
Ownership interest (as a percent)					91.00%
Ownership percentage of Equity Method Investment						32.00%
Number of full service retail locations operated	10			10
Number of full service retail locations acquired	2
Penske Truck Leasing Co., L.P.
Interim Financial Statements
Limited partnership interest (as a percent)	9.00%
Revenues \| Geographic \| U.S. and Puerto Rico
Interim Financial Statements
Automotive dealership revenue (as a percent)	60.00%
Revenues \| Geographic \| Outside the U.S.
Interim Financial Statements
Automotive dealership revenue (as a percent)	40.00%
Revenues \| Premium brands
Interim Financial Statements
Automotive dealership revenue (as a percent)	72.00%