Condensed Consolidating Financial Information - Statement of Cash Flows (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	$ 320.5	$ 270.6
Investing activities:
Purchase of equipment and improvements	(113.4)	(136.7)
Acquisitions, net	(431.9)	(65.4)
Other	15.0	(25.0)
Net cash used in continuing investing activities	(530.3)	(227.1)
Financing activities:
Issuance of 5.50% senior subordinated notes		500.0
Net borrowings of long-term debt	137.9	(99.1)
Net borrowings (repayments) of floor plan notes payable—non-trade	131.3	(163.0)
Payment of debt issuance costs		(6.6)
Repurchases of common stock	(8.5)	(173.6)
Dividends	(52.4)	(46.4)
Other	(5.8)	(15.9)
Net cash provided by (used in) continuing financing activities	202.5	(4.6)
Net cash provided by discontinued operations	2.5	2.9
Effect of exchange rate changes on cash and cash equivalents	1.5	(6.7)
Net change in cash and cash equivalents	(3.3)	35.1
Cash and cash equivalents, beginning of period	24.0	62.4
Cash and cash equivalents, end of period	20.7	97.5
Reportable legal entities | Penske Automotive Group
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	(50.5)	(84.0)
Investing activities:
Purchase of equipment and improvements	(1.4)	(0.4)
Other	6.0
Net cash used in continuing investing activities	4.6	(0.4)
Financing activities:
Issuance of 5.50% senior subordinated notes		500.0
Net borrowings of long-term debt	83.0	(160.0)
Net borrowings (repayments) of floor plan notes payable—non-trade	29.6	(149.7)
Payment of debt issuance costs		(6.6)
Repurchases of common stock	(8.5)	(173.6)
Dividends	(52.4)	(46.4)
Other	(5.8)	(6.1)
Distributions from (to) parent		126.8
Net cash provided by (used in) continuing financing activities	45.9	84.4
Reportable legal entities | Guarantor Subsidiaries
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	252.6	109.5
Investing activities:
Purchase of equipment and improvements	(49.4)	(149.9)
Acquisitions, net	(316.9)	(65.1)
Other	9.0	0.4
Net cash used in continuing investing activities	(357.3)	(214.6)
Financing activities:
Net borrowings of long-term debt	10.8	36.9
Net borrowings (repayments) of floor plan notes payable—non-trade	80.2	209.3
Other		(5.2)
Distributions from (to) parent	3.7	(125.0)
Net cash provided by (used in) continuing financing activities	94.7	116.0
Net cash provided by discontinued operations	2.5	0.3
Net change in cash and cash equivalents	(7.5)	11.2
Cash and cash equivalents, beginning of period	9.4
Cash and cash equivalents, end of period	1.9	11.2
Reportable legal entities | Non-Guarantor Subsidiaries
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	118.4	245.1
Investing activities:
Purchase of equipment and improvements	(62.6)	13.6
Acquisitions, net	(115.0)	(0.3)
Other		(25.4)
Net cash used in continuing investing activities	(177.6)	(12.1)
Financing activities:
Net borrowings of long-term debt	44.1	24.0
Net borrowings (repayments) of floor plan notes payable—non-trade	21.5	(222.6)
Other		(4.6)
Distributions from (to) parent	(3.7)	(1.8)
Net cash provided by (used in) continuing financing activities	61.9	(205.0)
Net cash provided by discontinued operations		2.6
Effect of exchange rate changes on cash and cash equivalents	1.5	(6.7)
Net change in cash and cash equivalents	4.2	23.9
Cash and cash equivalents, beginning of period	14.6	62.4
Cash and cash equivalents, end of period	$ 18.8	$ 86.3