Annual report pursuant to Section 13 and 15(d)

Business Acquisitions and Dispositions - Additional Information (Detail)

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Business Acquisitions and Dispositions - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2013
Franchise
Dealerships
Dec. 31, 2012
Dealerships
Dec. 31, 2011
Dealerships
Business Acquisition Pro Forma Information [Line Items]      
Aggregate cost of acquisitions during term of agreement $ 175,000,000    
Purchase price for franchise operations and underlying assets, including real estate, acquired 88,184,000      
Number of luxury franchises 2    
Goodwill 476,315,000 454,224,000 468,465,000
Disposed dealerships 0 10 0
Cash generated from disposition   72,200,000  
Interest allocated to discontinued operations 0 700,000 1,200,000
2013 Acquisitions [Member]
     
Business Acquisition Pro Forma Information [Line Items]      
Net assets relating to dealership operations 46,600,000    
Indefinite life intangible assets representing rights acquired under franchise agreements 19,500,000    
Goodwill $ 22,100,000