Summary of Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Data
Total revenues	$ 4,921.3	$ 4,960.1	$ 4,920.6	$ 4,482.9	$ 4,425.6	$ 4,396.7	$ 4,384.5	$ 4,025.2	$ 19,284.9	$ 17,232.0	$ 14,482.5
Gross profit	717.1	729.2	731.3	689.9	660.1	647.6	656.4	615.1	2,867.5	2,579.2	2,201.0
Net income	71.3	87.5	95.7	75.9	73.2	75.1	73.9	67.9	330.4	290.1	245.7
Net income attributable to Penske Automotive Group common stockholders	$ 70.3	$ 86.6	$ 94.0	$ 75.2	$ 71.8	$ 74.5	$ 72.9	$ 67.5	$ 326.1	$ 286.7	$ 244.2
Diluted earnings per share attributable to Penske Automotive Group common stockholders (in dollars per share)	$ 0.78	$ 0.96	$ 1.04	$ 0.83	$ 0.80	$ 0.83	$ 0.81	$ 0.75	$ 3.63	$ 3.17	$ 2.70