Condensed Consolidating Financial Information - Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Condensed consolidating statement of income
Revenues	$ 5,564.4	$ 5,746.9
Cost of sales	4,712.9	4,882.5
Gross profit	851.5	864.4
Selling, general and administrative expenses	666.4	663.1
Depreciation	26.4	25.6
Operating income	158.7	175.7
Floor plan interest expense	(21.8)	(18.9)
Other interest expense	(29.9)	(29.8)
Equity in earnings of affiliates	26.8	17.3
Income from continuing operations before income taxes	133.8	144.3
Income taxes	(34.7)	(36.6)
Income from continuing operations	99.1	107.7
Income (loss) income from discontinued operations, net of tax	0.1	0.1
Net income	99.2	107.8
Other comprehensive income, net of tax	8.5	31.8
Comprehensive income	107.7	139.6
Less: Comprehensive (loss) income attributable to non-controlling interests	(1.3)	(0.3)
Comprehensive income attributable to Penske Automotive Group common stockholders	109.0	139.9
Eliminations
Condensed consolidating statement of income
Equity in earnings of subsidiaries	(137.1)	(157.9)
Income from continuing operations before income taxes	(137.1)	(157.9)
Income taxes	35.3	40.0
Income from continuing operations	(101.8)	(117.9)
Income (loss) income from discontinued operations, net of tax	(0.1)	(0.1)
Net income	(101.9)	(118.0)
Other comprehensive income, net of tax	(6.9)	(31.5)
Comprehensive income	(108.8)	(149.5)
Less: Comprehensive (loss) income attributable to non-controlling interests	0.3
Comprehensive income attributable to Penske Automotive Group common stockholders	(109.1)	(149.5)
Penske Automotive Group | Reportable legal entities
Condensed consolidating statement of income
Selling, general and administrative expenses	6.6	6.5
Depreciation	0.3	0.4
Operating income	(6.9)	(6.9)
Floor plan interest expense	(1.8)	(1.6)
Other interest expense	(19.2)	(20.8)
Equity in earnings of affiliates	25.8	16.0
Equity in earnings of subsidiaries	137.1	157.9
Income from continuing operations before income taxes	135.0	144.6
Income taxes	(34.8)	(36.6)
Income from continuing operations	100.2	108.0
Income (loss) income from discontinued operations, net of tax	0.1	0.1
Net income	100.3	108.1
Other comprehensive income, net of tax	8.5	31.8
Comprehensive income	108.8	139.9
Less: Comprehensive (loss) income attributable to non-controlling interests	(0.3)
Comprehensive income attributable to Penske Automotive Group common stockholders	109.1	139.9
Guarantor Subsidiaries | Reportable legal entities
Condensed consolidating statement of income
Revenues	2,851.4	2,856.5
Cost of sales	2,382.9	2,395.2
Gross profit	468.5	461.3
Selling, general and administrative expenses	358.4	343.0
Depreciation	14.5	13.6
Operating income	95.6	104.7
Floor plan interest expense	(15.0)	(11.3)
Other interest expense	(3.0)	(1.9)
Income from continuing operations before income taxes	77.6	91.5
Income taxes	(23.0)	(25.2)
Income from continuing operations	54.6	66.3
Income (loss) income from discontinued operations, net of tax	0.1	0.1
Net income	54.7	66.4
Comprehensive income	54.7	66.4
Comprehensive income attributable to Penske Automotive Group common stockholders	54.7	66.4
Non-Guarantor Subsidiaries | Reportable legal entities
Condensed consolidating statement of income
Revenues	2,713.0	2,890.4
Cost of sales	2,330.0	2,487.3
Gross profit	383.0	403.1
Selling, general and administrative expenses	301.4	313.6
Depreciation	11.6	11.6
Operating income	70.0	77.9
Floor plan interest expense	(5.0)	(6.0)
Other interest expense	(7.7)	(7.1)
Equity in earnings of affiliates	1.0	1.3
Income from continuing operations before income taxes	58.3	66.1
Income taxes	(12.2)	(14.8)
Income from continuing operations	46.1	51.3
Net income	46.1	51.3
Other comprehensive income, net of tax	6.9	31.5
Comprehensive income	53.0	82.8
Less: Comprehensive (loss) income attributable to non-controlling interests	(1.3)	(0.3)
Comprehensive income attributable to Penske Automotive Group common stockholders	$ 54.3	$ 83.1