Inventories (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Inventories
Interest credits and advertising assistance	$ 9.1	$ 8.8

Floor plan interest credits and advertising assistance received from vendors, which reduce the cost of sales.

No definition available.

Name:	pag_FloorPlanInterestCreditsAndAdvertisingAssistance
Namespace Prefix:	pag_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration