CONSOLIDATED CONDENSED STATEMENTS OF EQUITY - USD ($) $ in Millions	Total Stockholders' Equity Attributable to Penske Automotive Group Cumulative Effect, Period of Adoption, Adjustment	Total Stockholders' Equity Attributable to Penske Automotive Group	Common Stock	Additional Paid-in Capital	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Non-controlling Interest	Cumulative Effect, Period of Adoption, Adjustment	Total
Balance at Dec. 31, 2018		$ 2,609.1		$ 477.8		$ 2,365.8	$ (234.5)	$ 25.6		$ 2,634.7
Balance (in shares) at Dec. 31, 2018			84,546,970
Increase (decrease) in stockholders' equity
Equity compensation		13.5		13.5						13.5
Equity compensation (in shares)			506,793
Repurchases of common stock		(174.1)		(174.1)						(174.1)
Repurchases of common stock (in shares)			(3,986,836)
Dividends		(97.3)				(97.3)				(97.3)
Purchase of subsidiary shares from non-controlling interest								(4.8)		(4.8)
Distributions to non-controlling interest								(0.5)		(0.5)
Foreign currency translation		(53.4)					(53.4)	(0.7)		(54.1)
Other		1.9					1.9	1.0		2.9
Net income		334.2				334.2		(0.4)		333.8
Balance (ASC 842) at Sep. 30, 2019	$ 5.0				$ 5.0				$ 5.0
Balance at Sep. 30, 2019		2,638.9		317.2		2,607.7	(286.0)	20.2		2,659.1
Balance (in shares) at Sep. 30, 2019			81,066,927
Balance at Jun. 30, 2019		2,640.5		356.5		2,524.3	(240.3)	20.5		2,661.0
Balance (in shares) at Jun. 30, 2019			81,956,305
Increase (decrease) in stockholders' equity
Equity compensation		4.3		4.3						4.3
Equity compensation (in shares)			132,244
Repurchases of common stock		(43.6)		(43.6)						(43.6)
Repurchases of common stock (in shares)			(1,021,622)
Dividends		(32.8)				(32.8)				(32.8)
Distributions to non-controlling interest								(0.1)		(0.1)
Foreign currency translation		(43.8)					(43.8)	(0.5)		(44.3)
Other		(1.9)					(1.9)	0.4		(1.5)
Net income		116.2				116.2		(0.1)		116.1
Balance (ASC 842) at Sep. 30, 2019	$ 5.0				$ 5.0				$ 5.0
Balance at Sep. 30, 2019		2,638.9		317.2		2,607.7	(286.0)	20.2		2,659.1
Balance (in shares) at Sep. 30, 2019			81,066,927
Balance at Dec. 31, 2019		2,793.4		320.4		2,675.8	(202.8)	18.2		2,811.6
Balance (in shares) at Dec. 31, 2019			81,084,751
Increase (decrease) in stockholders' equity
Equity compensation		15.2		15.2						15.2
Equity compensation (in shares)			279,196
Repurchases of common stock		(34.4)		(34.4)						(34.4)
Repurchases of common stock (in shares)			(1,027,736)
Dividends		(34.2)				(34.2)				(34.2)
Interest rate swaps		(4.0)					(4.0)			(4.0)
Foreign currency translation		(15.7)					(15.7)	0.3		(15.4)
Other		0.6					0.6	0.2		0.8
Net income		343.4				343.4		0.5		343.9
Balance at Sep. 30, 2020		3,064.3		301.2		2,985.0	(221.9)	19.2		3,083.5
Balance (in shares) at Sep. 30, 2020			80,336,211
Balance at Jun. 30, 2020		2,759.9		296.3		2,738.4	(274.8)	17.7		2,777.6
Balance (in shares) at Jun. 30, 2020			80,339,909
Increase (decrease) in stockholders' equity
Equity compensation		5.1		5.1						5.1
Equity compensation (in shares)			750
Repurchases of common stock		(0.2)		(0.2)						(0.2)
Repurchases of common stock (in shares)			(4,448)
Interest rate swaps		0.1					0.1			0.1
Foreign currency translation		49.5					49.5	0.4		49.9
Other		3.3					3.3	0.1		3.4
Net income		246.6				246.6		1.0		247.6
Balance at Sep. 30, 2020		$ 3,064.3		$ 301.2		$ 2,985.0	$ (221.9)	$ 19.2		$ 3,083.5
Balance (in shares) at Sep. 30, 2020			80,336,211