Condensed Consolidating Financial Information - Cash Flows (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	$ 304.6	$ 417.0
Investing activities:
Purchase of equipment and improvements	(134.5)	(118.8)
Proceeds from sale of dealerships	7.2	58.4
Proceeds from sale-leaseback transactions	7.3	5.8
Acquisitions, net	(1.1)	(168.6)
Other	(0.9)	(3.0)
Net cash used in continuing investing activities	(122.0)	(226.2)
Financing activities:
Net borrowings (repayments) of long-term debt	9.8	23.1
Net borrowings (repayments) of floor plan notes payable - non-trade	6.8	(92.9)
Repurchases of common stock	(130.6)	(55.8)
Dividends	(64.5)	(59.0)
Other	0.4	(6.1)
Net cash used in by continuing financing activities	(178.1)	(190.7)
Net cash (used in) provided by discontinued operations		0.2
Effect of exchange rate changes on cash and cash equivalents	(0.1)	(0.2)
Net change in cash and cash equivalents	4.4	0.1
Cash and cash equivalents, beginning of period	39.4	45.7
Cash and cash equivalents, end of period	43.8	45.8
Penske Automotive Group | Reportable legal entities
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	(18.4)	(24.5)
Investing activities:
Purchase of equipment and improvements	(0.7)	(0.4)
Other	(1.3)	(1.9)
Net cash used in continuing investing activities	(2.0)	(2.3)
Financing activities:
Net borrowings (repayments) of long-term debt	39.9	(73.0)
Net borrowings (repayments) of floor plan notes payable - non-trade	(6.4)	1.8
Repurchases of common stock	(130.6)	(55.8)
Dividends	(64.5)	(59.0)
Other	0.4	(0.3)
Distributions from (to) parent	181.6	213.1
Net cash used in by continuing financing activities	20.4	26.8
Guarantor Subsidiaries | Reportable legal entities
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	214.0	357.2
Investing activities:
Purchase of equipment and improvements	(56.0)	(68.4)
Proceeds from sale of dealerships	7.2	55.9
Net cash used in continuing investing activities	(48.8)	(12.5)
Financing activities:
Net borrowings (repayments) of long-term debt	37.0	(56.5)
Net borrowings (repayments) of floor plan notes payable - non-trade	(32.8)	(98.8)
Other		(5.8)
Distributions from (to) parent	(179.8)	(198.2)
Net cash used in by continuing financing activities	(175.6)	(359.3)
Net cash (used in) provided by discontinued operations		0.2
Net change in cash and cash equivalents	(10.4)	(14.4)
Cash and cash equivalents, beginning of period	12.9	14.8
Cash and cash equivalents, end of period	2.5	0.4
Non-Guarantor Subsidiaries | Reportable legal entities
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	109.0	84.3
Investing activities:
Purchase of equipment and improvements	(77.8)	(50.0)
Proceeds from sale of dealerships		2.5
Proceeds from sale-leaseback transactions	7.3
Acquisitions, net	(1.1)	(168.6)
Other	0.4	(1.1)
Net cash used in continuing investing activities	(71.2)	(211.4)
Financing activities:
Net borrowings (repayments) of long-term debt	(67.1)	152.6
Net borrowings (repayments) of floor plan notes payable - non-trade	46.0	4.1
Distributions from (to) parent	(1.8)	(14.9)
Net cash used in by continuing financing activities	(22.9)	141.8
Effect of exchange rate changes on cash and cash equivalents	(0.1)	(0.2)
Net change in cash and cash equivalents	14.8	14.5
Cash and cash equivalents, beginning of period	26.5	30.9
Cash and cash equivalents, end of period	$ 41.3	$ 45.4