Condensed Consolidating Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Condensed consolidating balance sheet
Cash and cash equivalents	$ 37.2	$ 24.0	$ 89.4	$ 62.4
Accounts receivable, net	938.8	879.0
Inventories	3,770.3	3,408.2
Other current assets	96.5	73.9
Assets held for sale		8.4
Total current assets	4,842.8	4,393.5
Property and equipment, net	2,091.4	1,806.5
Intangible assets	2,133.7	1,711.3
Equity method investments	1,184.9	893.4
Other long-term assets	29.5	28.3
Total assets	10,282.3	8,833.0
Floor plan notes payable	2,222.3	2,084.5
Floor plan notes payable - non-trade	1,388.5	1,233.3
Accounts payable	609.0	497.4
Accrued expenses	388.5	360.0
Current portion of long-term debt	67.6	48.3
Liabilities held for sale	0.7	6.1
Total current liabilities	4,676.6	4,229.6
Long-term debt	2,170.5	1,828.8
Deferred tax liabilities	771.6	564.6
Other long-term liabilities	551.6	430.5
Total liabilities	8,170.3	7,053.5
Total equity	2,112.0	1,779.5
Total liabilities and equity	$ 10,282.3	$ 8,833.0
3.75% senior subordinated notes due 2020
Condensed consolidating balance sheet
Interest rate (as a percent)	3.75%
Domestic Subsidiaries ownership guaranteeing obligations (as a percent)	100.00%
5.75% senior subordinated notes due 2022
Condensed consolidating balance sheet
Interest rate (as a percent)	5.75%	5.75%
Domestic Subsidiaries ownership guaranteeing obligations (as a percent)	100.00%
5.375% senior Subordinated Notes Due 2024
Condensed consolidating balance sheet
Interest rate (as a percent)	5.375%	5.375%
Domestic Subsidiaries ownership guaranteeing obligations (as a percent)	100.00%
5.50% senior subordinated notes due 2026
Condensed consolidating balance sheet
Interest rate (as a percent)	5.50%	5.50%
Domestic Subsidiaries ownership guaranteeing obligations (as a percent)	100.00%
Eliminations
Condensed consolidating balance sheet
Accounts receivable, net	$ (458.9)	$ (447.0)
Total current assets	(458.9)	(447.0)
Other long-term assets	(2,596.4)	(2,215.0)
Total assets	(3,055.3)	(2,662.0)
Accrued expenses	(458.9)	(447.0)
Total current liabilities	(458.9)	(447.0)
Long-term debt	(182.1)	(175.8)
Total liabilities	(641.0)	(622.8)
Total equity	(2,414.3)	(2,039.2)
Total liabilities and equity	(3,055.3)	(2,662.0)
Reportable legal entities | Penske Automotive Group
Condensed consolidating balance sheet
Accounts receivable, net	458.9	447.0
Other current assets	6.3	14.3
Total current assets	465.2	461.3
Property and equipment, net	3.6	3.3
Equity method investments	1,118.8	833.7
Other long-term assets	2,601.8	2,220.6
Total assets	4,189.4	3,518.9
Floor plan notes payable - non-trade	219.7	156.0
Accounts payable	4.1	4.9
Accrued expenses	1.0	0.9
Total current liabilities	224.8	161.8
Long-term debt	1,852.6	1,577.6
Total liabilities	2,077.4	1,739.4
Total equity	2,112.0	1,779.5
Total liabilities and equity	4,189.4	3,518.9
Reportable legal entities | Guarantor Subsidiaries
Condensed consolidating balance sheet
Cash and cash equivalents		9.4	1.3
Accounts receivable, net	420.8	483.6
Inventories	1,876.7	1,830.5
Other current assets	18.7	14.6
Assets held for sale		8.4
Total current assets	2,316.2	2,346.5
Property and equipment, net	1,007.6	961.0
Intangible assets	1,334.8	1,079.6
Other long-term assets	4.5	4.1
Total assets	4,663.1	4,391.2
Floor plan notes payable	1,104.7	1,178.0
Floor plan notes payable - non-trade	634.0	623.2
Accounts payable	161.2	171.9
Accrued expenses	43.3	77.2
Current portion of long-term debt	5.4	6.0
Liabilities held for sale	0.7	6.1
Total current liabilities	1,949.3	2,062.4
Long-term debt	193.8	186.0
Deferred tax liabilities	765.9	560.9
Other long-term liabilities	59.0	65.2
Total liabilities	2,968.0	2,874.5
Total equity	1,695.1	1,516.7
Total liabilities and equity	4,663.1	4,391.2
Reportable legal entities | Non-Guarantor Subsidiaries
Condensed consolidating balance sheet
Cash and cash equivalents	37.2	14.6	$ 88.1	$ 62.4
Accounts receivable, net	518.0	395.4
Inventories	1,893.6	1,577.7
Other current assets	71.5	45.0
Total current assets	2,520.3	2,032.7
Property and equipment, net	1,080.2	842.2
Intangible assets	798.9	631.7
Equity method investments	66.1	59.7
Other long-term assets	19.6	18.6
Total assets	4,485.1	3,584.9
Floor plan notes payable	1,117.6	906.5
Floor plan notes payable - non-trade	534.8	454.1
Accounts payable	443.7	320.6
Accrued expenses	803.1	728.9
Current portion of long-term debt	62.2	42.3
Total current liabilities	2,961.4	2,452.4
Long-term debt	306.2	241.0
Deferred tax liabilities	5.7	3.7
Other long-term liabilities	492.6	365.3
Total liabilities	3,765.9	3,062.4
Total equity	719.2	522.5
Total liabilities and equity	$ 4,485.1	$ 3,584.9