Long-Term Debt (Restrictions And Covenants) (Details) (USD $)	Sep. 30, 2013
Debt Instrument [Line Items]
The maximum of amount of letters of credit excluded from the leverage ratio calculation	$ 150,000,000
Capitalization ratio calculation, additions to shareholders' equity	$ 1,520,000,000
Debt Covenant, Maximum Required Ratio [Member]
Debt Instrument [Line Items]
Debt covenant capitalization ratio	65.00%
Debt covenant leverage ratio	3.75

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