Condensed Consolidating Financial Information - Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed consolidating statement of income
Revenues	$ 5,524.4	$ 5,152.0	$ 15,988.9	$ 15,230.7
Cost of sales	4,701.8	4,407.8	13,574.7	12,991.4
Gross profit	822.6	744.2	2,414.2	2,239.3
Selling, general and administrative expenses	646.1	581.2	1,869.8	1,722.8
Depreciation	24.3	21.5	70.0	66.8
Operating income	152.2	141.5	474.4	449.7
Floor plan interest expense	(16.4)	(11.9)	(45.6)	(37.8)
Other interest expense	(27.8)	(25.1)	(79.2)	(61.8)
Equity in earnings of affiliates	30.9	25.6	70.9	43.1
Income from continuing operations before income taxes	138.9	130.1	420.5	393.2
Income taxes	(44.7)	(41.7)	(136.0)	(128.4)
Income from continuing operations	94.2	88.4	284.5	264.8
Income (loss) from discontinued operations, net of tax	0.1	0.1	(0.3)	(1.1)
Net income	94.3	88.5	284.2	263.7
Other comprehensive income (loss), net of tax	35.3	(10.8)	101.9	(65.1)
Comprehensive income	129.6	77.7	386.1	198.6
Less: Comprehensive income attributable to non-controlling interests	0.6	1.3	3.8	4.5
Comprehensive income attributable to Penske Automotive Group common stockholders	129.0	76.4	382.3	194.1
Eliminations
Condensed consolidating statement of income
Equity in earnings of subsidiaries	(136.3)	(127.8)	(428.6)	(412.8)
Income from continuing operations before income taxes	(136.3)	(127.8)	(428.6)	(412.8)
Income taxes	43.8	41.4	139.0	136.1
Income from continuing operations	(92.5)	(86.4)	(289.6)	(276.7)
Income (loss) from discontinued operations, net of tax	(0.1)	(0.1)	0.3	1.1
Net income	(92.6)	(86.5)	(289.3)	(275.6)
Other comprehensive income (loss), net of tax	(31.9)	10.2	(93.0)	66.2
Comprehensive income	(124.5)	(76.3)	(382.3)	(209.4)
Less: Comprehensive income attributable to non-controlling interests	(0.8)	(0.3)	(2.8)	(1.1)
Comprehensive income attributable to Penske Automotive Group common stockholders	(123.7)	(76.0)	(379.5)	(208.3)
Reportable legal entities | Penske Automotive Group
Condensed consolidating statement of income
Selling, general and administrative expenses	6.3	3.9	18.5	15.2
Depreciation	0.4	0.5	1.2	1.3
Operating income	(6.7)	(4.4)	(19.7)	(16.5)
Floor plan interest expense	(1.3)	(0.7)	(3.4)	(2.0)
Other interest expense	(19.8)	(18.0)	(54.1)	(43.6)
Equity in earnings of affiliates	30.5	24.4	68.2	39.1
Equity in earnings of subsidiaries	136.3	127.8	428.6	412.8
Income from continuing operations before income taxes	139.0	129.1	419.6	389.8
Income taxes	(44.7)	(41.7)	(136.0)	(128.4)
Income from continuing operations	94.3	87.4	283.6	261.4
Income (loss) from discontinued operations, net of tax	0.1	0.1	(0.3)	(1.1)
Net income	94.4	87.5	283.3	260.3
Other comprehensive income (loss), net of tax	35.3	(10.8)	101.9	(65.1)
Comprehensive income	129.7	76.7	385.2	195.2
Less: Comprehensive income attributable to non-controlling interests	0.8	0.3	2.8	1.1
Comprehensive income attributable to Penske Automotive Group common stockholders	128.9	76.4	382.4	194.1
Reportable legal entities | Guarantor Subsidiaries
Condensed consolidating statement of income
Revenues	3,047.0	2,896.9	8,749.7	8,113.9
Cost of sales	2,570.2	2,457.1	7,351.8	6,856.0
Gross profit	476.8	439.8	1,397.9	1,257.9
Selling, general and administrative expenses	354.4	337.3	1,037.3	955.8
Depreciation	13.4	12.4	39.3	34.8
Operating income	109.0	90.1	321.3	267.3
Floor plan interest expense	(9.8)	(7.1)	(27.9)	(21.3)
Other interest expense	(2.3)	(2.2)	(6.6)	(2.8)
Income from continuing operations before income taxes	96.9	80.8	286.8	243.2
Income taxes	(36.0)	(32.2)	(109.8)	(97.9)
Income from continuing operations	60.9	48.6	177.0	145.3
Income (loss) from discontinued operations, net of tax	0.1	0.1	(0.3)	(1.0)
Net income	61.0	48.7	176.7	144.3
Comprehensive income	61.0	48.7	176.7	144.3
Comprehensive income attributable to Penske Automotive Group common stockholders	61.0	48.7	176.7	144.3
Reportable legal entities | Non-Guarantor Subsidiaries
Condensed consolidating statement of income
Revenues	2,477.4	2,255.1	7,239.2	7,116.8
Cost of sales	2,131.6	1,950.7	6,222.9	6,135.4
Gross profit	345.8	304.4	1,016.3	981.4
Selling, general and administrative expenses	285.4	240.0	814.0	751.8
Depreciation	10.5	8.6	29.5	30.7
Operating income	49.9	55.8	172.8	198.9
Floor plan interest expense	(5.3)	(4.1)	(14.3)	(14.5)
Other interest expense	(5.7)	(4.9)	(18.5)	(15.4)
Equity in earnings of affiliates	0.4	1.2	2.7	4.0
Income from continuing operations before income taxes	39.3	48.0	142.7	173.0
Income taxes	(7.8)	(9.2)	(29.2)	(38.2)
Income from continuing operations	31.5	38.8	113.5	134.8
Income (loss) from discontinued operations, net of tax				(0.1)
Net income	31.5	38.8	113.5	134.7
Other comprehensive income (loss), net of tax	31.9	(10.2)	93.0	(66.2)
Comprehensive income	63.4	28.6	206.5	68.5
Less: Comprehensive income attributable to non-controlling interests	0.6	1.3	3.8	4.5
Comprehensive income attributable to Penske Automotive Group common stockholders	$ 62.8	$ 27.3	$ 202.7	$ 64.0