Commitments and Contingent Liabilities - Leases (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingent Liabilities
Rent expense	$ 232.0	$ 232.1	$ 225.4
Aggregate rent paid by the tenants	24.4
Aggregate rent currently guaranteed by the Company	214.3
Letters of credit outstanding	41.9
Surety bonds posted	$ 19.8

Represents the aggregate rent currently guaranteed by entity under property lease guarantee.

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

Represents the aggregate rent paid by the tenants under property lease guaranteed by entity.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

- References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41499-112717

+ Details

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Balance Type:	debit
Period Type:	duration