Unaudited Condensed Consolidated Income Statements - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
TOTAL REVENUE	$ 5,224.3	$ 4,788.5	$ 10,168.5	$ 9,152.0
TOTAL COST OF SALES (excluding depreciation shown below)	4,405.2	4,043.6	8,549.5	7,699.7
TOTAL GROSS PROFIT	819.1	744.9	1,619.0	1,452.3
Selling, general, and administrative expenses	568.7	524.6	1,126.3	1,025.3
Depreciation and amortization	32.1	26.2	60.8	51.8
Other income, net	(3.8)	(3.7)	(5.1)	(11.7)
OPERATING INCOME	222.1	197.8	437.0	386.9
Non-operating income (expense) items:
Floorplan interest expense	(14.2)	(13.3)	(27.4)	(26.5)
Other interest expense	(21.6)	(21.3)	(43.0)	(42.9)
Interest income	0.0	0.1	0.1	0.1
Other income, net	0.5	0.9	1.6	2.4
INCOME FROM CONTINUING OPERATIONS BEFORE INCOME TAXES	186.8	164.2	368.3	320.0
Income tax provision	71.6	63.5	141.4	123.8
NET INCOME FROM CONTINUING OPERATIONS	115.2	100.7	226.9	196.2
Loss from discontinued operations, net of income taxes	(0.1)	(0.3)	(0.3)	(0.7)
NET INCOME	$ 115.1	$ 100.4	$ 226.6	$ 195.5
BASIC EARNINGS (LOSS) PER SHARE:
Continuing operations (in dollars per share)	$ 1.01	$ 0.85	$ 2.00	$ 1.64
Discontinued operations (in dollars per share)	0.00	0.00	0.00	(0.01)
Net income (in dollars per share)	$ 1.01	$ 0.84	$ 1.99	$ 1.64
Weighted average common shares outstanding (in shares)	113.8	119.1	113.7	119.3
DILUTED EARNINGS (LOSS) PER SHARE:
Continuing operations (in dollars per share)	$ 1.00	$ 0.83	$ 1.97	$ 1.62
Discontinued operations (in dollars per share)	0.00	0.00	0.00	(0.01)
Net income (in dollars per share)	$ 1.00	$ 0.83	$ 1.97	$ 1.61
Weighted average common shares outstanding (in shares)	115.1	120.8	115.1	121.1
COMMON SHARES OUTSTANDING, net of treasury stock, at period end (in shares)	113.4	118.5	113.4	118.5
New Vehicle [Member]
TOTAL REVENUE	$ 2,967.8	$ 2,736.9	$ 5,737.4	$ 5,165.5
TOTAL COST OF SALES (excluding depreciation shown below)	2,801.7	2,575.3	5,409.8	4,858.0
TOTAL GROSS PROFIT	166.1	161.6	327.6	307.5
Used Vehicle [Member]
TOTAL REVENUE	1,216.3	1,082.3	2,409.5	2,132.0
TOTAL COST OF SALES (excluding depreciation shown below)	1,125.2	993.0	2,214.7	1,948.4
TOTAL GROSS PROFIT	91.1	89.3	194.8	183.6
Parts and Service [Member]
TOTAL REVENUE	777.8	704.8	1,521.2	1,375.8
TOTAL COST OF SALES (excluding depreciation shown below)	440.6	404.0	864.0	788.3
TOTAL GROSS PROFIT	337.2	300.8	657.2	587.5
Finance and Insurance, Net [Member]
TOTAL REVENUE	217.7	185.4	425.3	357.8
TOTAL GROSS PROFIT	217.7	185.4	425.3	357.8
Other Goods and Services [Member]
TOTAL REVENUE	44.7	79.1	75.1	120.9
TOTAL COST OF SALES (excluding depreciation shown below)	37.7	71.3	61.0	105.0
TOTAL GROSS PROFIT	$ 7.0	$ 7.8	$ 14.1	$ 15.9