Condensed Consolidating Financial Information - Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Condensed consolidating statement of income
Revenues	$ 5,755.8	$ 5,940.3	$ 11,320.2	$ 11,687.2
Cost of sales	4,888.0	5,050.5	9,600.9	9,933.0
Gross profit	867.8	889.8	1,719.3	1,754.2
Selling, general and administrative expenses	668.9	675.4	1,335.3	1,338.5
Depreciation	27.1	25.7	53.5	51.3
Operating income	171.8	188.7	330.5	364.4
Floor plan interest expense	(21.0)	(19.9)	(42.8)	(38.8)
Other interest expense	(30.4)	(28.6)	(60.3)	(58.4)
Equity in earnings of affiliates	39.5	36.0	66.3	53.3
Income from continuing operations before income taxes	159.9	176.2	293.7	320.5
Income taxes	(41.5)	(41.0)	(76.2)	(77.6)
Income from continuing operations	118.4	135.2	217.5	242.9
Income (loss) income from discontinued operations, net of tax	0.1		0.2	0.1
Net income	118.5	135.2	217.7	243.0
Other comprehensive income, net of tax	(14.5)	(72.8)	(6.0)	(41.0)
Comprehensive income	104.0	62.4	211.7	202.0
Less: Comprehensive income (loss) attributable to non-controlling interests	0.8	(0.5)	(0.5)	(0.8)
Comprehensive income attributable to Penske Automotive Group common stockholders	103.2	62.9	212.2	202.8
Eliminations
Condensed consolidating statement of income
Equity in earnings of subsidiaries	(150.0)	(168.3)	(287.1)	(325.9)
Income from continuing operations before income taxes	(150.0)	(168.3)	(287.1)	(325.9)
Income taxes	39.1	39.4	74.4	79.2
Income from continuing operations	(110.9)	(128.9)	(212.7)	(246.7)
Income (loss) income from discontinued operations, net of tax	(0.1)		(0.2)	(0.1)
Net income	(111.0)	(128.9)	(212.9)	(246.8)
Other comprehensive income, net of tax	17.2	68.1	10.3	36.6
Comprehensive income	(93.8)	(60.8)	(202.6)	(210.2)
Less: Comprehensive income (loss) attributable to non-controlling interests	(0.2)	1.1	0.1	1.1
Comprehensive income attributable to Penske Automotive Group common stockholders	(93.6)	(61.9)	(202.7)	(211.3)
Penske Automotive Group | Reportable legal entities
Condensed consolidating statement of income
Selling, general and administrative expenses	6.8	6.6	13.4	12.8
Depreciation	0.4	0.4	0.7	0.8
Operating income	(7.2)	(7.0)	(14.1)	(13.6)
Floor plan interest expense	(2.4)	(1.8)	(4.2)	(3.4)
Other interest expense	(19.3)	(18.9)	(38.5)	(39.7)
Equity in earnings of affiliates	38.0	35.0	63.8	51.0
Equity in earnings of subsidiaries	150.0	168.3	287.1	325.9
Income from continuing operations before income taxes	159.1	175.6	294.1	320.2
Income taxes	(41.5)	(41.0)	(76.3)	(77.6)
Income from continuing operations	117.6	134.6	217.8	242.6
Income (loss) income from discontinued operations, net of tax	0.1		0.2	0.1
Net income	117.7	134.6	218.0	242.7
Other comprehensive income, net of tax	(14.5)	(72.8)	(6.0)	(41.0)
Comprehensive income	103.2	61.8	212.0	201.7
Less: Comprehensive income (loss) attributable to non-controlling interests	0.2	(1.1)	(0.1)	(1.1)
Comprehensive income attributable to Penske Automotive Group common stockholders	103.0	62.9	212.1	202.8
Guarantor Subsidiaries | Reportable legal entities
Condensed consolidating statement of income
Revenues	3,127.6	3,071.8	5,979.0	5,928.3
Cost of sales	2,628.9	2,582.3	5,011.8	4,977.5
Gross profit	498.7	489.5	967.2	950.8
Selling, general and administrative expenses	364.5	359.7	722.9	703.0
Depreciation	14.6	13.7	29.1	27.3
Operating income	119.6	116.1	215.2	220.5
Floor plan interest expense	(14.3)	(12.3)	(29.3)	(23.6)
Other interest expense	(3.0)	(2.0)	(6.0)	(3.9)
Income from continuing operations before income taxes	102.3	101.8	179.9	193.0
Income taxes	(29.5)	(27.4)	(52.5)	(52.4)
Income from continuing operations	72.8	74.4	127.4	140.6
Income (loss) income from discontinued operations, net of tax	0.1		0.2	0.1
Net income	72.9	74.4	127.6	140.7
Comprehensive income	72.9	74.4	127.6	140.7
Comprehensive income attributable to Penske Automotive Group common stockholders	72.9	74.4	127.6	140.7
Non-Guarantor Subsidiaries | Reportable legal entities
Condensed consolidating statement of income
Revenues	2,628.2	2,868.5	5,341.2	5,758.9
Cost of sales	2,259.1	2,468.2	4,589.1	4,955.5
Gross profit	369.1	400.3	752.1	803.4
Selling, general and administrative expenses	297.6	309.1	599.0	622.7
Depreciation	12.1	11.6	23.7	23.2
Operating income	59.4	79.6	129.4	157.5
Floor plan interest expense	(4.3)	(5.8)	(9.3)	(11.8)
Other interest expense	(8.1)	(7.7)	(15.8)	(14.8)
Equity in earnings of affiliates	1.5	1.0	2.5	2.3
Income from continuing operations before income taxes	48.5	67.1	106.8	133.2
Income taxes	(9.6)	(12.0)	(21.8)	(26.8)
Income from continuing operations	38.9	55.1	85.0	106.4
Net income	38.9	55.1	85.0	106.4
Other comprehensive income, net of tax	(17.2)	(68.1)	(10.3)	(36.6)
Comprehensive income	21.7	(13.0)	74.7	69.8
Less: Comprehensive income (loss) attributable to non-controlling interests	0.8	(0.5)	(0.5)	(0.8)
Comprehensive income attributable to Penske Automotive Group common stockholders	$ 20.9	$ (12.5)	$ 75.2	$ 70.6