Business Combinations - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Summary of unaudited consolidated pro forma results of operations
Revenues	$ 7,930.8	$ 8,075.6
Net income attributable to Penske Automotive Group common stockholders	$ 234.9	$ 258.1
Net income per diluted common share (in dollars per share)	$ 3.57	$ 3.86