Revenues - Other Disclosures (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Revenues
Total revenues	$ 5,773.8	$ 5,009.1
Commercial Vehicle Distribution and Other
Revenues
Total revenues	$ 132.2	101.1
Vehicle Sales | Retail Automotive and Retail Commercial Truck Dealership
Revenues
Payment period	30 days
Service and parts | Retail Automotive and Retail Commercial Truck Dealership
Revenues
Payment period	30 days
Finance and insurance, net | Retail Automotive and Retail Commercial Truck Dealership
Revenues
Payment period	30 days
Aggregate reserves relating to chargeback activity	$ 29.4		$ 28.7
Penske Australia | Commercial Vehicle Distribution and Other
Revenues
Payment period	30 days
Penske Australia | Service and parts | Commercial Vehicle Distribution and Other
Revenues
Total revenues	$ 61.4	$ 58.4