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 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

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

Number of brands represented by franchises awarded to the reporting entity.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of franchises disposed of during the period.

+ References

No definition available.

+ Details

Name:	pag_NumberOfFranchisesDisposedOf
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 truck retail dealerships owned by the reporting entity.

+ References

No definition available.

+ Details

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

- Definition

Represents the total amount of receivables from manufacturers as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	pag_ReceivablesFromManufacturer
Namespace Prefix:	pag_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	pag_SummaryOfSignificantAccountingPoliciesLineItems
Namespace Prefix:	pag_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 30

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 30

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

In a business combination achieved in stages, this element represents the amount of gain recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (g)(2)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

Name:	us-gaap_ConcentrationRiskPercentage1
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

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Data Type:	num:percentItemType
Balance Type:	na
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- 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

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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_
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Organization and Summary of Significant Accounting Policies (Details) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended				0 Months Ended		3 Months Ended	12 Months Ended					2 Months Ended	12 Months Ended		1 Months Ended	12 Months Ended
	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2014 USD ($) item	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2014 Bremen, Germany item	Oct. 01, 2014 MTU Detroit Diesel Australia USD ($)	Oct. 01, 2014 MTU Detroit Diesel Australia AUD	Dec. 31, 2014 MTU Detroit Diesel Australia USD ($)	Dec. 31, 2014 Commercial Vehicle Distribution item	Dec. 31, 2014 Commercial Vehicle Distribution Revenues	Dec. 31, 2014 Commercial Vehicle Distribution Gross Profit Member	Dec. 31, 2014 Penske Truck Leasing Co., L.P.	Dec. 31, 2014 Retail Automotive Dealership USD ($) item	Dec. 31, 2014 Retail Commercial Vehicle Dealership USD ($)	Dec. 31, 2014 Retail Commercial Vehicle Dealership USD ($)	Sep. 30, 2014 Retail Commercial Vehicle Dealership	Feb. 28, 2015 Retail Commercial Vehicle Dealership Subsequent event item	Dec. 31, 2014 Commercial Vehicle Distribution And Other Operations USD ($)	Dec. 31, 2014 BMW,MINI item	Dec. 31, 2014 BMW,MINI Revenues	Dec. 31, 2014 Audi/Volkswagen/Porsche/Bentley Revenues	Dec. 31, 2014 Toyota/Lexus/Scion Revenues	Dec. 31, 2014 Mercedes-Benz/Sprinter/smart Revenues
Organization and Summary of Significant Accounting Policies
Total revenues	$ 4,410.1us-gaap_SalesRevenueNet	$ 4,381.4us-gaap_SalesRevenueNet	$ 4,370.5us-gaap_SalesRevenueNet	$ 4,015.2us-gaap_SalesRevenueNet	$ 3,793.3us-gaap_SalesRevenueNet	$ 3,724.6us-gaap_SalesRevenueNet	$ 3,599.2us-gaap_SalesRevenueNet	$ 3,326.8us-gaap_SalesRevenueNet	$ 17,177.2us-gaap_SalesRevenueNet	$ 14,443.9us-gaap_SalesRevenueNet	$ 12,902.6us-gaap_SalesRevenueNet				$ 52.5					$ 16,600.0	$ 125.6				$ 448.9
Receivables from manufacturers	169.9pag_ReceivablesFromManufacturer				145.8pag_ReceivablesFromManufacturer				169.9pag_ReceivablesFromManufacturer	145.8pag_ReceivablesFromManufacturer
Significant Accounting Policies
Total number of owned and operated franchises																				327
Number of owned and operated franchises in US																				179
Number of owned and operated franchises outside US																				148
Percentage of total																	2.30%	2.40%									27.00%	22.00%	15.00%	11.00%
Gain on investment									16.0													16.0
Number of acquired franchises									2pag_NumberOfFranchisesAcquired
Number of franchises awarded to the reporting entity									6
Number of franchises disposed of									7pag_NumberOfFranchisesDisposedOf			4
Sales to external customer	4,410.1us-gaap_SalesRevenueNet	4,381.4us-gaap_SalesRevenueNet	4,370.5us-gaap_SalesRevenueNet	4,015.2us-gaap_SalesRevenueNet	3,793.3us-gaap_SalesRevenueNet	3,724.6us-gaap_SalesRevenueNet	3,599.2us-gaap_SalesRevenueNet	3,326.8us-gaap_SalesRevenueNet	17,177.2us-gaap_SalesRevenueNet	14,443.9us-gaap_SalesRevenueNet	12,902.6us-gaap_SalesRevenueNet				52.5					16,600.0	125.6				448.9
Number of operating franchises																								16		8
Minimum number of dealership locations																70
Limited partnership interest (as a percent)																			9.00%
Purchase price													$ 115.0	131.5								$ 75.3
Ownership interest (as a percent)																					91.00%	91.00%				50.00%
Number of full service retail locations operated																								10
Number of full service retail locations acquired																								2
Number of retail dealerships owned by the reporting entity																3
Ownership percentage of Equity Method Investment																							32.00%