Business Combinations - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Summary of unaudited consolidated pro forma results of operations
Revenues	$ 7,465.1	$ 7,069.9	$ 22,418.6	$ 21,484.8
Net income attributable to Penske Automotive Group common stockholders	$ 263.7	$ 342.4	$ 866.0	$ 1,094.0
Net income per diluted common share (in dollars per share)	$ 3.92	$ 4.64	$ 12.69	$ 14.47