Business Combinations - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Summary of unaudited consolidated pro forma results of operations
Revenues	$ 8,415.6	$ 8,166.0	$ 24,859.7	$ 24,397.0
Net income attributable to Penske Automotive Group common stockholders	$ 220.8	$ 224.9	$ 716.2	$ 750.1
Net income per diluted common share (in dollars per share)	$ 3.36	$ 3.41	$ 10.89	$ 11.31