Interim Financial Statements (Details)	Sep. 30, 2012 stores franchises
Interim Financial Statements [Abstract]
Owned and operated new vehicle franchises	261
Number of stores	215

Represents the number of owned and operated new vehicle franchises.

No definition available.

Name:	an_OwnedAndOperatedNewVehicleFranchises
Namespace Prefix:	an_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant