Acquisitions and Dispositions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012 Dealerships	Mar. 31, 2011 Dealerships
Acquisitions and Dispositions (Additional Textual) [Abstract]
Number of dealerships acquired	3
Acquisitions and Dispositions (Textual) [Abstract]
Consideration paid for acquisitions	55.3	35.0
Kansas [Member]
Acquisitions and Dispositions (Additional Textual) [Abstract]
Number of dealerships acquired	1
Texas [Member]
Acquisitions and Dispositions (Additional Textual) [Abstract]
Number of dealerships acquired	1	2
South Carolina [Member]
Acquisitions and Dispositions (Additional Textual) [Abstract]
Number of dealerships acquired	1

Amount of cash paid to acquire the entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph f(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionCostOfAcquiredEntityCashPaid
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant