Condensed Consolidating Financial Information - Statement of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	$ 457.2	$ 373.4
Investing activities:
Purchase of equipment and improvements	(171.7)	(151.1)
Acquisition of additional ownership interest in Penske Truck Leasing	(498.5)
Acquisitions, net	(106.0)	(85.4)
Other	(9.5)	0.2
Net cash used in continuing investing activities	(785.7)	(236.3)
Financing activities:
Net borrowings (repayments) of long-term debt	119.3	(165.7)
Net borrowings (repayments) of floor plan notes payable—non-trade	12.8	94.6
Issuance of 5.50% senior subordinated notes	500.0
Payment of debt issuance costs	(6.7)	(1.8)
Repurchases of common stock	(173.6)	(22.0)
Dividends	(70.3)	(62.3)
Other	(9.7)	(5.9)
Net cash provided by (used in) continuing financing activities	371.8	(163.1)
Net cash provided by discontinued operations	3.0	39.7
Effect of exchange rate changes on cash and cash equivalents	(19.3)	(0.3)
Net change in cash and cash equivalents	27.0	13.4
Cash and cash equivalents, beginning of period	62.4	36.3
Cash and cash equivalents, end of period	89.4	49.7
Reportable legal entities | Penske Automotive Group
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	(30.2)	28.4
Investing activities:
Purchase of equipment and improvements	(0.8)	(1.0)
Acquisition of additional ownership interest in Penske Truck Leasing	(498.5)
Net cash used in continuing investing activities	(499.3)	(1.0)
Financing activities:
Net borrowings (repayments) of long-term debt	45.0	(10.0)
Net borrowings (repayments) of floor plan notes payable—non-trade	4.2	66.9
Issuance of 5.50% senior subordinated notes	500.0
Payment of debt issuance costs	(6.7)
Repurchases of common stock	(173.6)	(22.0)
Dividends	(70.3)	(62.3)
Distributions from (to) parent	230.9
Net cash provided by (used in) continuing financing activities	529.5	(27.4)
Reportable legal entities | Guarantor Subsidiaries
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	90.7	154.3
Investing activities:
Purchase of equipment and improvements	(103.5)	(74.0)
Acquisitions, net		(21.7)
Other	17.0
Net cash used in continuing investing activities	(86.5)	(95.7)
Financing activities:
Net borrowings (repayments) of long-term debt	8.4	24.0
Net borrowings (repayments) of floor plan notes payable—non-trade	215.5	(130.1)
Distributions from (to) parent	(227.4)	8.3
Net cash provided by (used in) continuing financing activities	(3.5)	(97.8)
Net cash provided by discontinued operations	0.6	39.2
Net change in cash and cash equivalents	1.3
Cash and cash equivalents, end of period	1.3
Reportable legal entities | Non-Guarantor Subsidiaries
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	396.7	190.7
Investing activities:
Purchase of equipment and improvements	(67.4)	(76.1)
Acquisitions, net	(106.0)	(63.7)
Other	(26.5)	0.2
Net cash used in continuing investing activities	(199.9)	(139.6)
Financing activities:
Net borrowings (repayments) of long-term debt	65.9	(179.7)
Net borrowings (repayments) of floor plan notes payable—non-trade	(206.9)	157.8
Payment of debt issuance costs		(1.8)
Other	(9.7)	(5.9)
Distributions from (to) parent	(3.5)	(8.3)
Net cash provided by (used in) continuing financing activities	(154.2)	(37.9)
Net cash provided by discontinued operations	2.4	0.5
Effect of exchange rate changes on cash and cash equivalents	(19.3)	(0.3)
Net change in cash and cash equivalents	25.7	13.4
Cash and cash equivalents, beginning of period	62.4	36.3
Cash and cash equivalents, end of period	$ 88.1	$ 49.7