Annual report pursuant to Section 13 and 15(d)

Business Acquisitions and Dispositions - Additional Information (Detail)

v3.6.0.2
Business Acquisitions and Dispositions - Additional Information (Detail)
$ in Millions
 12 Months Ended
Dec. 31, 2016
USD ($)
Dealerships
Franchise
Business
Dec. 31, 2015
USD ($)
Dealerships
Franchise
Dec. 31, 2014
USD ($)
Dealerships
Franchise
Business Acquisition [Line Items]      
Number of businesses acquired   0  
Business acquisition, consideration amount | $     $ 50.9
Number of franchises disposed | Dealerships 0 4 9
Cash generated from disposition | $   $ 8.0 $ 74.8
Number of franchises classified as held for sale 0    
Franchised Dealerships [Member]      
Business Acquisition [Line Items]      
Number of businesses opened | Business 2    
Echo Park [Member]      
Business Acquisition [Line Items]      
Number of businesses opened | Business 2    
Stand-alone Used Vehicle Dealership Business and Real Estate [Member]      
Business Acquisition [Line Items]      
Number of businesses acquired | Business 3    
Business acquisition, consideration amount | $ $ 15.9    
Luxury Franchise [Member]      
Business Acquisition [Line Items]      
Number of businesses acquired     2
Mid-line Import Franchise [Member]      
Business Acquisition [Line Items]      
Number of businesses acquired     1
Domestic Franchise [Member]      
Business Acquisition [Line Items]      
Number of businesses acquired     1