Unaudited Condensed Consolidated Income Statements - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
TOTAL REVENUE	$ 5,353.7	$ 4,909.0	$ 15,522.2	$ 14,061.0
TOTAL COST OF SALES (excluding depreciation shown below)	4,523.4	4,156.1	13,072.9	11,855.8
TOTAL GROSS PROFIT	830.3	752.9	2,449.3	2,205.2
Selling, general, and administrative expenses	568.7	522.3	1,695.0	1,547.6
Depreciation and amortization	32.9	27.2	93.7	79.0
Other income, net	(7.0)	(4.0)	(12.1)	(15.7)
OPERATING INCOME	235.7	207.4	672.7	594.3
Non-operating income (expense) items:
Floorplan interest expense	(14.7)	(13.1)	(42.1)	(39.6)
Other interest expense	(21.4)	(21.7)	(64.4)	(64.6)
Interest income	0.0	0.1	0.1	0.2
Other income (loss), net	(4.3)	1.1	(2.7)	3.5
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	195.3	173.8	563.6	493.8
Income tax provision	76.3	67.1	217.7	190.9
NET INCOME FROM CONTINUING OPERATIONS	119.0	106.7	345.9	302.9
Loss from discontinued operations, net of income taxes	(0.5)	(0.2)	(0.8)	(0.9)
NET INCOME	$ 118.5	$ 106.5	$ 345.1	$ 302.0
BASIC EARNINGS (LOSS) PER SHARE:
Continuing operations (in dollars per share)	$ 1.06	$ 0.91	$ 3.05	$ 2.56
Discontinued operations (in dollars per share)	0.00	0.00	(0.01)	(0.01)
Net income (in dollars per share)	$ 1.05	$ 0.91	$ 3.05	$ 2.55
Weighted average common shares outstanding (in shares)	112.4	117.0	113.3	118.5
DILUTED EARNINGS (LOSS) PER SHARE:
Continuing operations (in dollars per share)	$ 1.05	$ 0.90	$ 3.02	$ 2.52
Discontinued operations (in dollars per share)	0.00	0.00	(0.01)	(0.01)
Net income (in dollars per share)	$ 1.04	$ 0.90	$ 3.01	$ 2.51
Weighted average common shares outstanding (in shares)	113.6	118.5	114.6	120.2
COMMON SHARES OUTSTANDING, net of treasury stock, at period end (in shares)	111.0	114.5	111.0	114.5
New Vehicle [Member]
TOTAL REVENUE	$ 3,113.6	$ 2,823.6	$ 8,851.0	$ 7,989.1
TOTAL COST OF SALES (excluding depreciation shown below)	2,942.8	2,666.5	8,352.6	7,524.5
TOTAL GROSS PROFIT	170.8	157.1	498.4	464.6
Used Vehicle [Member]
TOTAL REVENUE	1,205.4	1,148.5	3,614.9	3,280.5
TOTAL COST OF SALES (excluding depreciation shown below)	1,122.2	1,060.1	3,336.9	3,008.5
TOTAL GROSS PROFIT	83.2	88.4	278.0	272.0
Parts and Service [Member]
TOTAL REVENUE	783.3	717.4	2,304.5	2,093.2
TOTAL COST OF SALES (excluding depreciation shown below)	441.1	413.7	1,305.1	1,202.0
TOTAL GROSS PROFIT	342.2	303.7	999.4	891.2
Finance and Insurance, Net [Member]
TOTAL REVENUE	227.1	196.5	652.4	554.3
TOTAL GROSS PROFIT	227.1	196.5	652.4	554.3
Other Goods and Services [Member]
TOTAL REVENUE	24.3	23.0	99.4	143.9
TOTAL COST OF SALES (excluding depreciation shown below)	17.3	15.8	78.3	120.8
TOTAL GROSS PROFIT	$ 7.0	$ 7.2	$ 21.1	$ 23.1