Condensed Consolidating Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 02, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed consolidating balance sheet
Cash and cash equivalents	$ 28.1		$ 39.4	$ 45.7	$ 24.0
Accounts receivable, net	960.3		929.1
Inventories	4,260.7		4,040.1
Other current assets	85.0		86.6
Total current assets	5,334.1		5,095.2
Property and equipment, net	2,366.4		2,250.0
Operating lease right-of-use assets	2,360.5	$ 2,425.6
Intangible assets	2,463.2		2,238.2
Equity method investments	1,399.0		1,305.2
Other long-term assets	19.5		15.9
Total assets	13,942.7		10,904.5
Floor plan notes payable	2,412.5		2,362.2
Floor plan notes payable - non-trade	1,594.0		1,428.6
Accounts payable	638.8		598.2
Accrued expenses and other current liabilities	701.9	636.8	566.6
Current portion of long-term debt	103.3		92.0
Liabilities held for sale	0.5		0.7
Total current liabilities	5,451.0		5,048.3
Long-term debt	2,257.0		2,124.7
Long-term operating lease liabilities	2,301.2	2,387.5
Deferred tax liabilities	677.9	578.7	577.8
Other long-term liabilities	444.0	$ 481.0	519.0
Total liabilities	11,131.1		8,269.8
Total equity	2,811.6		2,634.7	$ 2,428.0	1,779.5
Total liabilities and equity	$ 13,942.7		$ 10,904.5
5.75% senior subordinated notes due 2022
Condensed consolidating balance sheet
Interest rate (as a percent)	5.75%		5.75%	5.75%
5.375% senior subordinated notes due 2024
Condensed consolidating balance sheet
Interest rate (as a percent)	5.375%		5.375%	5.375%
5.50% senior subordinated notes due 2026
Condensed consolidating balance sheet
Interest rate (as a percent)	5.50%		5.50%	5.50%
3.75% senior subordinated notes due 2020
Condensed consolidating balance sheet
Interest rate (as a percent)	3.75%		3.75%	3.75%
Guarantor Subsidiaries
Condensed consolidating balance sheet
Domestic Subsidiaries ownership guaranteeing obligations (as a percent)	100.00%
Eliminations
Condensed consolidating balance sheet
Accounts receivable, net	$ (497.4)		$ (481.7)
Total current assets	(497.4)		(481.7)
Other long-term assets	(2,984.3)		(2,814.3)
Total assets	(3,481.7)		(3,296.0)
Accrued expenses and other current liabilities	(497.4)		(481.7)
Total current liabilities	(497.4)		(481.7)
Long-term debt	(96.8)		(88.6)
Total liabilities	(594.2)		(570.3)
Total equity	(2,887.5)		(2,725.7)
Total liabilities and equity	(3,481.7)		(3,296.0)
Reportable legal entities | Penske Automotive Group
Condensed consolidating balance sheet
Accounts receivable, net	497.4		481.7
Other current assets	3.7		10.6
Total current assets	501.1		492.3
Property and equipment, net	3.7		3.9
Operating lease right-of-use assets	9.3
Equity method investments	1,328.8		1,239.9
Other long-term assets	2,996.2		2,821.0
Total assets	4,839.1		4,557.1
Floor plan notes payable - non-trade	233.9		232.3
Accounts payable	6.0		4.9
Accrued expenses and other current liabilities	1.6		1.4
Current portion of long-term debt	13.0
Total current liabilities	254.5		238.6
Long-term debt	1,757.9		1,683.8
Long-term operating lease liabilities	8.9
Other long-term liabilities	6.2
Total liabilities	2,027.5		1,922.4
Total equity	2,811.6		2,634.7
Total liabilities and equity	4,839.1		4,557.1
Reportable legal entities | Guarantor Subsidiaries
Condensed consolidating balance sheet
Cash and cash equivalents			12.9	$ 14.8	9.4
Accounts receivable, net	508.9		507.1
Inventories	2,124.9		1,961.6
Other current assets	22.7		17.8
Total current assets	2,656.5		2,499.4
Property and equipment, net	1,101.2		1,077.7
Operating lease right-of-use assets	1,574.7
Intangible assets	1,633.6		1,422.6
Other long-term assets	1.4		2.9
Total assets	6,967.4		5,002.6
Floor plan notes payable	1,427.1		1,348.3
Floor plan notes payable - non-trade	522.5		505.9
Accounts payable	226.9		196.6
Accrued expenses and other current liabilities	242.0		160.2
Current portion of long-term debt	10.7		6.3
Liabilities held for sale	0.5		0.7
Total current liabilities	2,429.7		2,218.0
Long-term debt	254.5		225.7
Long-term operating lease liabilities	1,545.6
Deferred tax liabilities	668.1		570.5
Other long-term liabilities	30.9		57.6
Total liabilities	4,928.8		3,071.8
Total equity	2,038.6		1,930.8
Total liabilities and equity	6,967.4		5,002.6
Reportable legal entities | Non-Guarantor Subsidiaries
Condensed consolidating balance sheet
Cash and cash equivalents	28.1		26.5	$ 30.9	$ 14.6
Accounts receivable, net	451.4		422.0
Inventories	2,135.8		2,078.5
Other current assets	58.6		58.2
Total current assets	2,673.9		2,585.2
Property and equipment, net	1,261.5		1,168.4
Operating lease right-of-use assets	776.5
Intangible assets	829.6		815.6
Equity method investments	70.2		65.3
Other long-term assets	6.2		6.3
Total assets	5,617.9		4,640.8
Floor plan notes payable	985.4		1,013.9
Floor plan notes payable - non-trade	837.6		690.4
Accounts payable	405.9		396.7
Accrued expenses and other current liabilities	955.7		886.7
Current portion of long-term debt	79.6		85.7
Total current liabilities	3,264.2		3,073.4
Long-term debt	341.4		303.8
Long-term operating lease liabilities	746.7
Deferred tax liabilities	9.8		7.3
Other long-term liabilities	406.9		461.4
Total liabilities	4,769.0		3,845.9
Total equity	848.9		794.9
Total liabilities and equity	$ 5,617.9		$ 4,640.8