Inventories (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Inventories
Interest credits and advertising assistance	$ 39.9	$ 34.1	$ 30.5

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