Business Combinations - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Summary of unaudited consolidated pro forma results of operations
Revenues	$ 7,615.8	$ 7,961.7	$ 23,240.7	$ 23,903.5
Net income attributable to Penske Automotive Group common stockholders	$ 226.6	$ 272.2	$ 692.8	$ 892.7
Net income per diluted common share (in dollars per share)	$ 3.39	$ 4.05	$ 10.35	$ 13.09