Condensed Consolidating Financial Information - Statement of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	$ 466.8	$ 463.3
Investing activities:
Purchase of equipment and improvements	(180.1)	(171.7)
Acquisition of additional ownership interest in Penske Truck Leasing	(239.1)	(498.5)
Acquisitions, net	(449.7)	(106.0)
Other	13.3	(9.5)
Net cash used in continuing investing activities	(855.6)	(785.7)
Financing activities:
Net borrowings (repayments) of long-term debt	50.3	119.3
Net borrowings (repayments) of floor plan notes payable — non-trade	155.2	12.8
Payment of debt issuance costs	(4.0)	(6.7)
Repurchases of common stock	(18.5)	(173.6)
Dividends	(80.1)	(70.3)
Other	(5.8)	(15.8)
Net cash provided by continuing financing activities	397.1	365.7
Net cash provided by discontinued operations	2.7	3.0
Effect of exchange rate changes on cash and cash equivalents	2.2	(19.3)
Net change in cash and cash equivalents	13.2	27.0
Cash and cash equivalents, beginning of period	24.0	62.4
Cash and cash equivalents, end of period	37.2	89.4
3.75% senior subordinated notes due 2020
Financing activities:
Issuance of senior subordinated notes	300.0
5.50% senior subordinated notes due 2026
Financing activities:
Issuance of senior subordinated notes		500.0
Reportable legal entities | Penske Automotive Group
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	(34.5)	(24.1)
Investing activities:
Purchase of equipment and improvements	(2.4)	(0.8)
Acquisition of additional ownership interest in Penske Truck Leasing	(239.1)	(498.5)
Other	4.6
Net cash used in continuing investing activities	(236.9)	(499.3)
Financing activities:
Net borrowings (repayments) of long-term debt	(24.0)	45.0
Net borrowings (repayments) of floor plan notes payable — non-trade	63.7	4.2
Payment of debt issuance costs	(4.0)	(6.7)
Repurchases of common stock	(18.5)	(173.6)
Dividends	(80.1)	(70.3)
Other	(5.8)	(6.1)
Distributions from (to) parent	40.1	230.9
Net cash provided by continuing financing activities	271.4	523.4
Reportable legal entities | Penske Automotive Group | 3.75% senior subordinated notes due 2020
Financing activities:
Issuance of senior subordinated notes	300.0
Reportable legal entities | Penske Automotive Group | 5.50% senior subordinated notes due 2026
Financing activities:
Issuance of senior subordinated notes		500.0
Reportable legal entities | Guarantor Subsidiaries
Condensed consolidating statement of cash flows
Net cash provided by (used in) continuing operating activities	359.5	90.7
Investing activities:
Purchase of equipment and improvements	(80.0)	(103.5)
Acquisitions, net	(316.9)
Other	9.0	17.0
Net cash used in continuing investing activities	(387.9)	(86.5)
Financing activities:
Net borrowings (repayments) of long-term debt	8.6	8.4
Net borrowings (repayments) of floor plan notes payable — non-trade	43.2	215.5
Distributions from (to) parent	(35.5)	(227.4)
Net cash provided by continuing financing activities	16.3	(3.5)
Net cash provided by discontinued operations	2.7	0.6
Net change in cash and cash equivalents	(9.4)	1.3
Cash and cash equivalents, beginning of period	9.4
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	141.8	396.7
Investing activities:
Purchase of equipment and improvements	(97.7)	(67.4)
Acquisitions, net	(132.8)	(106.0)
Other	(0.3)	(26.5)
Net cash used in continuing investing activities	(230.8)	(199.9)
Financing activities:
Net borrowings (repayments) of long-term debt	65.7	65.9
Net borrowings (repayments) of floor plan notes payable — non-trade	48.3	(206.9)
Other		(9.7)
Distributions from (to) parent	(4.6)	(3.5)
Net cash provided by continuing financing activities	109.4	(154.2)
Net cash provided by discontinued operations		2.4
Effect of exchange rate changes on cash and cash equivalents	2.2	(19.3)
Net change in cash and cash equivalents	22.6	25.7
Cash and cash equivalents, beginning of period	14.6	62.4
Cash and cash equivalents, end of period	$ 37.2	$ 88.1