Business And Credit Concentrations (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2015	Dec. 31, 2014
Risks and Uncertainties [Abstract]
Percentage of new vehicle sales from core brands	95.00%
Manufacturer receivables	$ 180.5	$ 198.3

The amount due to the company from manufacturers or distributors, within one year of the balance sheet date, including (1) rebates and assistance for holdbacks, floorplan interest and advertising expenses; (2) incentives based on achieving certain objectives; and (3) amounts due for warranty and service work performed for customers.

No definition available.

Name:	an_ManufacturerReceivables
Namespace Prefix:	an_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant