Related Party Transactions - Joint ventures (Details)		1 Months Ended		12 Months Ended
	Sep. 06, 2017	Jul. 31, 2016	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017
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				28.00%
Audi, Mercedes-Benz, Sprinter, Porsche | Fairfield, Connecticut
Related party transactions
Ownership percentage of Consolidated Entity				80.00%
Mercedes-Benz | Greenwich, Connecticut
Related party transactions
Ownership percentage of Consolidated Entity				80.00%
BMW, MINI, Maserati, Porsche, Audi, Land Rover, Volvo, Mercedes-Benz, smart and Lamborghini | Northern Italy
Related party transactions
Ownership percentage of Consolidated Entity				84.00%
Audi, Maserati, SEAT, Skoda, Volkswagen | Aachen, Germany
Related party transactions
Ownership percentage of Consolidated Entity				79.35%	68.00%
Additional ownership percentage acquired				11.40%
PTL
Related party transactions
Ownership interest in Penske Truck Leasing Co (as a percent)	23.40%	23.40%	9.00%	28.90%