Condensed Consolidating Financial Information - Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	$ 660.8	$ 535.9
Investing activities:
Purchase of equipment and improvements	(188.8)	(188.5)
Proceeds from sale of dealerships	7.3	58.4
Proceeds from sale-leaseback transactions	7.3	10.7
Acquisitions, net	(326.9)	(168.6)
Other	(2.3)	(3.5)
Net cash used in continuing investing activities	(503.4)	(291.5)
Financing activities:
Net borrowings (repayments) of long-term debt	170.3	(41.0)
Net (repayments) borrowings of floor plan notes payable - non-trade	(18.0)	(59.6)
Repurchases of common stock	(174.1)	(55.8)
Dividends	(97.3)	(89.7)
Other	0.1	(6.2)
Net cash used in by continuing financing activities	(119.0)	(252.3)
Net cash provided by discontinued operations	0.2	0.3
Effect of exchange rate changes on cash and cash equivalents	(0.5)	(0.5)
Net change in cash and cash equivalents	38.1	(8.1)
Cash and cash equivalents, beginning of period	39.4	45.7
Cash and cash equivalents, end of period	77.5	37.6
Penske Automotive Group | Reportable legal entities
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	(38.1)	16.1
Investing activities:
Purchase of equipment and improvements	(0.7)	(2.3)
Other	(2.6)	(2.4)
Net cash used in continuing investing activities	(3.3)	(4.7)
Financing activities:
Net borrowings (repayments) of long-term debt	144.9	(172.0)
Net (repayments) borrowings of floor plan notes payable - non-trade	(5.1)	(23.3)
Repurchases of common stock	(174.1)	(55.8)
Dividends	(97.3)	(89.7)
Other	0.1	(0.3)
Distributions from (to) parent	172.9	329.7
Net cash used in by continuing financing activities	41.4	(11.4)
Guarantor Subsidiaries | Reportable legal entities
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	457.0	356.2
Investing activities:
Purchase of equipment and improvements	(72.9)	(95.1)
Proceeds from sale of dealerships	7.3	55.9
Acquisitions, net	(325.8)
Net cash used in continuing investing activities	(391.4)	(39.2)
Financing activities:
Net borrowings (repayments) of long-term debt	34.1	41.6
Net (repayments) borrowings of floor plan notes payable - non-trade	9.5	(50.1)
Other		(5.9)
Distributions from (to) parent	(122.3)	(314.3)
Net cash used in by continuing financing activities	(78.7)	(328.7)
Net cash provided by discontinued operations	0.2	0.3
Net change in cash and cash equivalents	(12.9)	(11.4)
Cash and cash equivalents, beginning of period	12.9	14.8
Cash and cash equivalents, end of period	0.0	3.4
Non-Guarantor Subsidiaries | Reportable legal entities
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	241.9	163.6
Investing activities:
Purchase of equipment and improvements	(115.2)	(91.1)
Proceeds from sale of dealerships		2.5
Proceeds from sale-leaseback transactions	7.3	10.7
Acquisitions, net	(1.1)	(168.6)
Other	0.3	(1.1)
Net cash used in continuing investing activities	(108.7)	(247.6)
Financing activities:
Net borrowings (repayments) of long-term debt	(8.7)	89.4
Net (repayments) borrowings of floor plan notes payable - non-trade	(22.4)	13.8
Distributions from (to) parent	(50.6)	(15.4)
Net cash used in by continuing financing activities	(81.7)	87.8
Effect of exchange rate changes on cash and cash equivalents	(0.5)	(0.5)
Net change in cash and cash equivalents	51.0	3.3
Cash and cash equivalents, beginning of period	26.5	30.9
Cash and cash equivalents, end of period	$ 77.5	$ 34.2