Related Party Transactions - Joint ventures (Details) - item	1 Months Ended		3 Months Ended	12 Months Ended
	Oct. 31, 2016	Mar. 31, 2016	Sep. 30, 2015	Dec. 31, 2016	Sep. 30, 2016
Audi, Mercedes-Benz, Sprinter, Porsche, Smart | Fairfield, Connecticut
Related party transactions
Ownership percentage of Consolidated Entity				80.00%
Audi, Mercedes-Benz, Sprinter, Porsche, Smart | Fairfield, Connecticut | Lucio A. Noto
Related party transactions
Ownership percentage in joint venture				20.00%
Mercedes-Benz | Greenwich, Connecticut
Related party transactions
Ownership percentage of Consolidated Entity				80.00%
Mercedes-Benz | Greenwich, Connecticut | Lucio A. Noto
Related party transactions
Ownership percentage in joint venture				20.00%
BMW, MINI, Maserati, Porsche, Audi, Land Rover, Volvo and Nissan | Northern Italy
Related party transactions
Ownership percentage of Consolidated Entity	84.00%			84.00%	70.00%
Audi, Maserati, SEAT, Skoda, Volkswagen | Aachen, Germany
Related party transactions
Ownership percentage of Consolidated Entity				68.00%
Additional ownership percentage acquired		8.00%	10.00%
Lexus Toyota Volkswagen | Frankfurt, Germany
Related party transactions
Ownership percentage of equity method investment				50.00%
BMW, MINI | Barcelona Spain
Related party transactions
Ownership percentage of equity method investment				50.00%
BMW, MINI, Rolls-Royce, Ferrari and ALPINA | Tokyo, Japan
Related party transactions
Ownership percentage of equity method investment				49.00%
Penske Commercial Leasing Australia
Related party transactions
Ownership percentage of equity method investment				33.00%
Penske Vehicle Services
Related party transactions
Ownership percentage of equity method investment				31.00%
PTL
Related party transactions
Ownership percentage of equity method investment				23.40%
National Powersport Auctions
Related party transactions
Ownership percentage of equity method investment				7.00%
Retail Automotive Dealership
Related party transactions
Number of acquired franchises				20
Retail Automotive Dealership | Northern Italy
Related party transactions
Number of acquired franchises	7
Retail Automotive Dealership | Porsche Dealership | Northern Italy
Related party transactions
Number of acquired franchises	3
Retail Automotive Dealership | Audi Dealership | Northern Italy
Related party transactions
Number of acquired franchises	1
Retail Automotive Dealership | Land Rover Dealership | Northern Italy
Related party transactions
Number of acquired franchises	1
Retail Automotive Dealership | Volvo Dealership | Northern Italy
Related party transactions
Number of acquired franchises	1
Retail Automotive Dealership | Nissan Dealership | Northern Italy
Related party transactions
Number of acquired franchises	1