Long-Term Debt (Leverage Ratio And Capitalization Ratio Under The Terms Of The Amended Credit Agreement) (Details)	Sep. 30, 2012
Debt Covenant, Maximum Required Ratio [Member]
Leverage ratio	3.75
Capitalization ratio	65.00%
Debt Covenant, Actual Ratio [Member]
Leverage ratio	2.74
Capitalization ratio	56.40%

An amount contractually defined in the credit agreement as principally reflecting vehicle floorplan payable and non-vehicle debt divided by the company's total capitalization including vehicle floorplan payable and certain adjustments. Under the credit agreement, the company is required to remain in compliance with a maximum capitalization ratio.

No definition available.

Name:	an_DebtCovenantCapitalizationRatio
Namespace Prefix:	an_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant