Condensed Consolidating Financial Information - Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed consolidating statement of income
Revenues	$ 5,967.6	$ 5,658.6	$ 17,287.8	$ 17,345.8
Cost of sales	5,097.9	4,806.0	14,698.8	14,739.0
Gross profit	869.7	852.6	2,589.0	2,606.8
Selling, general and administrative expenses	672.8	662.8	2,008.1	2,001.3
Depreciation	27.5	25.9	81.0	77.2
Operating income	169.4	163.9	499.9	528.3
Floor plan interest expense	(21.4)	(20.2)	(64.2)	(59.0)
Other interest expense	(32.9)	(28.3)	(93.2)	(86.7)
Equity in earnings of affiliates	43.3	41.7	109.6	95.0
Income from continuing operations before income taxes	158.4	157.1	452.1	477.6
Income taxes	(42.4)	(27.1)	(118.6)	(104.7)
Income from continuing operations	116.0	130.0	333.5	372.9
Income (loss) income from discontinued operations, net of tax	0.1	0.1	0.3	0.2
Net income	116.1	130.1	333.8	373.1
Other comprehensive loss, net of tax	(46.2)	(17.5)	(52.2)	(58.5)
Comprehensive income	69.9	112.6	281.6	314.6
Less: Comprehensive income (loss) attributable to non-controlling interests	(0.6)	(0.2)	(1.1)	(1.0)
Comprehensive income attributable to Penske Automotive Group common stockholders	70.5	112.8	282.7	315.6
Eliminations
Condensed consolidating statement of income
Equity in earnings of subsidiaries	(149.2)	(144.2)	(436.3)	(470.1)
Income from continuing operations before income taxes	(149.2)	(144.2)	(436.3)	(470.1)
Income taxes	40.0	24.8	114.4	104.0
Income from continuing operations	(109.2)	(119.4)	(321.9)	(366.1)
Income (loss) income from discontinued operations, net of tax	(0.1)	(0.1)	(0.3)	(0.2)
Net income	(109.3)	(119.5)	(322.2)	(366.3)
Other comprehensive loss, net of tax	44.7	19.8	55.0	56.4
Comprehensive income	(64.6)	(99.7)	(267.2)	(309.9)
Less: Comprehensive income (loss) attributable to non-controlling interests	0.5	0.1	0.6	1.2
Comprehensive income attributable to Penske Automotive Group common stockholders	(65.1)	(99.8)	(267.8)	(311.1)
Penske Automotive Group | Reportable legal entities
Condensed consolidating statement of income
Selling, general and administrative expenses	6.6	6.3	20.0	19.1
Depreciation	0.3	0.4	1.0	1.2
Operating income	(6.9)	(6.7)	(21.0)	(20.3)
Floor plan interest expense	(1.9)	(1.9)	(6.1)	(5.3)
Other interest expense	(24.0)	(19.1)	(62.5)	(58.8)
Equity in earnings of affiliates	42.2	40.7	106.0	91.7
Equity in earnings of subsidiaries	149.2	144.2	436.3	470.1
Income from continuing operations before income taxes	158.6	157.2	452.7	477.4
Income taxes	(42.5)	(27.1)	(118.8)	(104.7)
Income from continuing operations	116.1	130.1	333.9	372.7
Income (loss) income from discontinued operations, net of tax	0.1	0.1	0.3	0.2
Net income	116.2	130.2	334.2	372.9
Other comprehensive loss, net of tax	(46.2)	(17.5)	(52.2)	(58.5)
Comprehensive income	70.0	112.7	282.0	314.4
Less: Comprehensive income (loss) attributable to non-controlling interests	(0.5)	(0.1)	(0.6)	(1.2)
Comprehensive income attributable to Penske Automotive Group common stockholders	70.5	112.8	282.6	315.6
Guarantor Subsidiaries | Reportable legal entities
Condensed consolidating statement of income
Revenues	3,478.6	3,061.9	9,457.6	8,990.2
Cost of sales	2,951.1	2,584.1	7,962.9	7,561.6
Gross profit	527.5	477.8	1,494.7	1,428.6
Selling, general and administrative expenses	375.1	356.6	1,098.0	1,059.6
Depreciation	15.2	14.0	44.3	41.3
Operating income	137.2	107.2	352.4	327.7
Floor plan interest expense	(14.7)	(12.7)	(44.0)	(36.3)
Other interest expense	(3.3)	(2.3)	(9.3)	(6.2)
Income from continuing operations before income taxes	119.2	92.2	299.1	285.2
Income taxes	(33.0)	(14.6)	(85.5)	(67.0)
Income from continuing operations	86.2	77.6	213.6	218.2
Income (loss) income from discontinued operations, net of tax	0.1	0.1	0.3	0.2
Net income	86.3	77.7	213.9	218.4
Comprehensive income	86.3	77.7	213.9	218.4
Comprehensive income attributable to Penske Automotive Group common stockholders	86.3	77.7	213.9	218.4
Non-Guarantor Subsidiaries | Reportable legal entities
Condensed consolidating statement of income
Revenues	2,489.0	2,596.7	7,830.2	8,355.6
Cost of sales	2,146.8	2,221.9	6,735.9	7,177.4
Gross profit	342.2	374.8	1,094.3	1,178.2
Selling, general and administrative expenses	291.1	299.9	890.1	922.6
Depreciation	12.0	11.5	35.7	34.7
Operating income	39.1	63.4	168.5	220.9
Floor plan interest expense	(4.8)	(5.6)	(14.1)	(17.4)
Other interest expense	(5.6)	(6.9)	(21.4)	(21.7)
Equity in earnings of affiliates	1.1	1.0	3.6	3.3
Income from continuing operations before income taxes	29.8	51.9	136.6	185.1
Income taxes	(6.9)	(10.2)	(28.7)	(37.0)
Income from continuing operations	22.9	41.7	107.9	148.1
Net income	22.9	41.7	107.9	148.1
Other comprehensive loss, net of tax	(44.7)	(19.8)	(55.0)	(56.4)
Comprehensive income	(21.8)	21.9	52.9	91.7
Less: Comprehensive income (loss) attributable to non-controlling interests	(0.6)	(0.2)	(1.1)	(1.0)
Comprehensive income attributable to Penske Automotive Group common stockholders	$ (21.2)	$ 22.1	$ 54.0	$ 92.7