Condensed Consolidating Financial Information (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed consolidating statement of income
Total revenues	$ 4,410.1	$ 4,381.4	$ 4,370.5	$ 4,015.2	$ 3,793.3	$ 3,724.6	$ 3,599.2	$ 3,326.8	$ 17,177.2	$ 14,443.9	$ 12,902.6
Cost of sales									14,603.5	12,246.9	10,927.0
Gross profit	658.7	646.2	654.8	614.0	571.0	558.4	547.8	519.8	2,573.7	2,197.0	1,975.6
Selling, general and administrative expenses									1,999.6	1,705.6	1,558.3
Depreciation									70.0	59.6	52.2
Operating income									504.1	431.8	365.1
Floor plan interest expense									(46.1)	(43.1)	(38.0)
Other interest expense									(52.8)	(45.2)	(46.1)
Equity in earnings of affiliates									40.8	30.7	27.6
Gain on investment									16.0
Debt redemption costs											(17.8)
Income from continuing operations before income taxes									462.0	374.2	290.8
Income taxes									(153.2)	(123.9)	(94.6)
Income from continuing operations									308.8	250.3	196.2
(Loss) income from discontinued operations, net of tax									(18.7)	(4.6)	(9.0)
Net income	73.2	75.1	73.9	67.9	59.7	65.5	62.5	58.0	290.1	245.7	187.2
Other comprehensive income (loss), net of taxes									(66.2)	18.9	17.6
Comprehensive income									223.9	264.6	204.8
Less: Comprehensive income attributable to the non-controlling interests									2.1	2.0	1.9
Comprehensive income attributable to Penske Automotive Group common stockholders									221.8	262.6	202.9
Eliminations
Condensed consolidating statement of income
Equity in earnings of subsidiaries									(473.2)	(406.1)	(341.8)
Income from continuing operations before income taxes									(473.2)	(406.1)	(341.8)
Income taxes									157.9	135.0	111.9
Income from continuing operations									(315.3)	(271.1)	(229.9)
(Loss) income from discontinued operations, net of tax									16.8	4.6	9.0
Net income									(298.5)	(266.5)	(220.9)
Other comprehensive income (loss), net of taxes									62.5	(9.8)	(16.6)
Comprehensive income									(236.0)	(276.3)	(237.5)
Less: Comprehensive income attributable to the non-controlling interests									1.4	(0.5)	(0.3)
Comprehensive income attributable to Penske Automotive Group common stockholders									(237.4)	(275.8)	(237.2)
Reportable legal entities | Penske Automotive Group
Condensed consolidating statement of income
Selling, general and administrative expenses									28.7	21.4	19.4
Depreciation									1.3	1.8	1.3
Operating income									(30.0)	(23.2)	(20.7)
Floor plan interest expense									(10.4)	(9.6)	(8.6)
Other interest expense									(29.8)	(26.1)	(29.5)
Equity in earnings of affiliates									36.5	25.5	24.0
Gain on investment									16.0
Debt redemption costs											(17.8)
Equity in earnings of subsidiaries									473.2	406.1	341.8
Income from continuing operations before income taxes									455.5	372.7	289.2
Income taxes									(152.0)	(123.9)	(94.6)
Income from continuing operations									303.5	248.8	194.6
(Loss) income from discontinued operations, net of tax									(16.8)	(4.6)	(9.0)
Net income									286.7	244.2	185.6
Other comprehensive income (loss), net of taxes									(66.2)	18.9	17.6
Comprehensive income									220.5	263.1	203.2
Less: Comprehensive income attributable to the non-controlling interests									(1.4)	0.5	0.3
Comprehensive income attributable to Penske Automotive Group common stockholders									221.9	262.6	202.9
Reportable legal entities | Guarantor Subsidiaries
Condensed consolidating statement of income
Total revenues									9,589.0	8,534.2	7,630.7
Cost of sales									8,092.5	7,178.5	6,424.2
Gross profit									1,496.5	1,355.7	1,206.5
Selling, general and administrative expenses									1,133.9	1,025.9	930.8
Depreciation									37.8	33.8	28.0
Operating income									324.8	296.0	247.7
Floor plan interest expense									(20.7)	(19.5)	(16.4)
Other interest expense									(5.0)	(1.9)
Income from continuing operations before income taxes									299.1	274.6	231.3
Income taxes									(110.3)	(100.4)	(87.7)
Income from continuing operations									188.8	174.2	143.6
(Loss) income from discontinued operations, net of tax									(2.4)	0.9	(0.5)
Net income									186.4	175.1	143.1
Other comprehensive income (loss), net of taxes									4.7	4.0	1.0
Comprehensive income									191.1	179.1	144.1
Comprehensive income attributable to Penske Automotive Group common stockholders									191.1	179.1	144.1
Reportable legal entities | Non-Guarantor Subsidiaries
Condensed consolidating statement of income
Total revenues									7,588.2	5,909.7	5,271.9
Cost of sales									6,511.0	5,068.4	4,502.8
Gross profit									1,077.2	841.3	769.1
Selling, general and administrative expenses									837.0	658.3	608.1
Depreciation									30.9	24.0	22.9
Operating income									209.3	159.0	138.1
Floor plan interest expense									(15.0)	(14.0)	(13.0)
Other interest expense									(18.0)	(17.2)	(16.6)
Equity in earnings of affiliates									4.3	5.2	3.6
Income from continuing operations before income taxes									180.6	133.0	112.1
Income taxes									(48.8)	(34.6)	(24.2)
Income from continuing operations									131.8	98.4	87.9
(Loss) income from discontinued operations, net of tax									(16.3)	(5.5)	(8.5)
Net income									115.5	92.9	79.4
Other comprehensive income (loss), net of taxes									(67.2)	5.8	15.6
Comprehensive income									48.3	98.7	95.0
Less: Comprehensive income attributable to the non-controlling interests									2.1	2.0	1.9
Comprehensive income attributable to Penske Automotive Group common stockholders									$ 46.2	$ 96.7	$ 93.1