Interim Financial Statements - Business Overview (Details) $ in Millions		1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 01, 2022 dealership	Feb. 28, 2022 dealership	Mar. 31, 2022 USD ($) dealership franchise location vehicle	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Jan. 01, 2022 USD ($)	Dec. 31, 2020 USD ($)
Interim Financial Statements
Total revenues			$ 6,975.4	$ 5,773.8
After-tax cumulative effect adjustment to retained earnings after adoption of Topic 842			4,164.4	3,484.7	$ 4,095.0		$ 3,326.1
Retained Earnings
Interim Financial Statements
After-tax cumulative effect adjustment to retained earnings after adoption of Topic 842			$ 4,336.9	3,299.2	4,196.6		$ 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)
Retail Automotive Franchise
Interim Financial Statements
Number of franchises disposed | franchise			0
PTL
Interim Financial Statements
Ownership interest in Penske Truck Leasing Co (as a percent)			28.90%
Number of vehicles in fleet | vehicle			373,000
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			137,000
Minimum number of vehicle brands offered | vehicle			35
Revenues | Geographic | U.S. and Puerto Rico
Interim Financial Statements
Automotive dealership revenue (as a percent)			55.00%
Revenues | Geographic | Outside the U.S.
Interim Financial Statements
Automotive dealership revenue (as a percent)			45.00%
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			$ 6,029.2	5,206.9	$ 22,500.0
Retail automotive dealership | Retail Automotive
Interim Financial Statements
Total number of owned and operated franchises | franchise			321
Number of owned and operated franchises in US | franchise			147
Number of owned and operated franchises outside US | franchise			174
Number of stand-alone used vehicle dealerships operated in United States and United Kingdom | dealership			23
Retail automotive dealership | U.S.
Interim Financial Statements
Total revenues			$ 3,343.6	3,004.8
Number of franchises awarded to the reporting entity | franchise			1
Number of acquired franchises | franchise			1
Retail automotive dealership | U.K.
Interim Financial Statements
Total revenues			$ 2,262.9	1,853.4
Retail automotive dealership | U.K. | BMW Mini | Subsequent Event
Interim Financial Statements
Number of locations acquired | dealership	3
Retail automotive dealership | U.K. | Mercedes Benz
Interim Financial Statements
Number of dealerships to be transitioned | dealership			14
Retail automotive dealership | Revenues | Premium brands
Interim Financial Statements
Automotive dealership revenue (as a percent)			70.00%
Retail automotive dealership | CarShop | U.S. | Retail Automotive
Interim Financial Statements
Number of retail locations operated | dealership			8
Retail automotive dealership | CarShop | U.K. | Retail Automotive
Interim Financial Statements
Number of retail locations operated | dealership			15
Retail commercial truck dealership
Interim Financial Statements
Total revenues			$ 792.3	$ 434.7
Retail commercial truck dealership | TEAM Truck Centres
Interim Financial Statements
Number of full service dealerships added | dealership		4
Retail commercial truck dealership | PTG | Retail Commercial Truck Dealership
Interim Financial Statements
Number of operating locations | location			41