Interim Financial Statements - Business Overview (Details) $ in Millions	1 Months Ended	3 Months Ended			6 Months Ended		12 Months Ended
	Feb. 28, 2022 dealership	Sep. 30, 2022 franchise	Jun. 30, 2022 USD ($) franchise dealership vehicle location	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) franchise dealership vehicle location	Jun. 30, 2021 USD ($) franchise	Dec. 31, 2021 USD ($)	Mar. 31, 2022 USD ($) location	Jan. 01, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Interim Financial Statements
Total revenues | $			$ 6,906.9	$ 6,987.5	$ 13,882.3	$ 12,761.3
After-tax cumulative effect adjustment to retained earnings after adoption of Topic 842 | $			4,219.4	3,762.7	4,219.4	3,762.7	$ 4,095.0	$ 4,164.4		$ 3,484.7	$ 3,326.1
Retained Earnings
Interim Financial Statements
After-tax cumulative effect adjustment to retained earnings after adoption of Topic 842 | $			$ 4,506.7	3,602.5	$ 4,506.7	3,602.5	4,196.6	$ 4,336.9		$ 3,299.2	$ 3,151.3
Cumulative Effect, Period of Adoption, Adjustment
Interim Financial Statements
After-tax cumulative effect adjustment to retained earnings after adoption of Topic 842 | $							(121.6)
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings
Interim Financial Statements
After-tax cumulative effect adjustment to retained earnings after adoption of Topic 842 | $							(121.6)
PTL
Interim Financial Statements
Ownership interest in Penske Truck Leasing Co (as a percent)					28.90%
Number of vehicles in fleet | vehicle			386,000		386,000
PTL | Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings
Interim Financial Statements
After-tax cumulative effect adjustment to retained earnings after adoption of Topic 842 | $									$ 121.6
Retail Automotive
Interim Financial Statements
Minimum number of vehicles retailed and wholesaled | vehicle					276,000
Minimum number of vehicle brands offered | vehicle					35
Revenues | Geographic | U.S. and Puerto Rico
Interim Financial Statements
Automotive dealership revenue (as a percent)					56.00%
Revenues | Geographic | Outside the U.S.
Interim Financial Statements
Automotive dealership revenue (as a percent)					44.00%
Penske Corporation | PTL
Interim Financial Statements
Ownership interest in Penske Truck Leasing Co (as a percent)					41.10%
Mitsui and Co | PTL
Interim Financial Statements
Ownership interest in Penske Truck Leasing Co (as a percent)					30.00%
Retail automotive dealership
Interim Financial Statements
Total revenues | $			$ 5,997.3	6,197.6	$ 12,026.5	11,404.5	$ 22,500.0
Retail automotive dealership | Retail Automotive
Interim Financial Statements
Total number of owned and operated franchises			332		332
Number of owned and operated franchises in US			152		152
Number of owned and operated franchises outside US			180		180
Number of stand-alone used vehicle dealerships operated in United States and United Kingdom | dealership			21		21
Retail automotive dealership | Mercedes Benz | Forecast
Interim Financial Statements
Number of acquired franchises		5
Retail automotive dealership | United States And United Kingdom | Retail Automotive
Interim Financial Statements
Number of acquired franchises					10
Retail automotive dealership | U.S.
Interim Financial Statements
Total revenues | $			$ 3,443.9	3,614.5	$ 6,787.5	$ 6,619.3
Number of franchises awarded to the reporting entity						1
Retail automotive dealership | U.S. | Retail Automotive
Interim Financial Statements
Number of retail locations operated | dealership					8
Number of acquired franchises					4
Number of franchises awarded to the reporting entity					2
Retail automotive dealership | U.K.
Interim Financial Statements
Total revenues | $			$ 2,196.4	2,190.6	$ 4,459.3	$ 4,044.0
Retail automotive dealership | U.K. | Retail Automotive
Interim Financial Statements
Number of retail locations operated | dealership					13
Number of acquired franchises | dealership					6
Number of retail locations disposed | dealership			2
Retail automotive dealership | U.K. | Mercedes Benz | Forecast
Interim Financial Statements
Number of acquired franchises		3
Retail automotive dealership | Revenues | Premium brands
Interim Financial Statements
Automotive dealership revenue (as a percent)					70.00%
Retail commercial truck dealership
Interim Financial Statements
Total revenues | $			$ 768.7	$ 625.3	$ 1,561.0	$ 1,060.0
Retail commercial truck dealership | TEAM Truck Centres
Interim Financial Statements
Number of full service dealerships added | dealership	4
Retail commercial truck dealership | Retail Commercial Truck Dealership
Interim Financial Statements
Minimum number of vehicles retailed and wholesaled					9,100
Number of operating locations | location			39		39			41
Number of franchises disposed			2
Retail commercial truck dealership | United States And Ontario, Canada
Interim Financial Statements
Number of dealerships | dealership			9		9