Annual report pursuant to Section 13 and 15(d)

Business Acquisitions and Dispositions - Additional Information (Detail)

v3.8.0.1
Business Acquisitions and Dispositions - Additional Information (Detail)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
USD ($)
Dealerships
Store
Franchise
Dec. 31, 2016
USD ($)
Dealerships
Business
Dec. 31, 2015
USD ($)
Dealerships
Franchise
Business Acquisition [Line Items]      
Goodwill acquired related to acquisition $ 60,024    
Number of businesses acquired | Franchise     0
Number of franchises disposed | Dealerships 3 0 4
Cash generated from disposition $ 38,200   $ 8,000
Number of franchises classified as held for sale | Franchise 0    
EchoPark Stores [Member]      
Business Acquisition [Line Items]      
Number of stores | Store 2    
Stand-Alone Pre-Owned Vehicle Store [Member]      
Business Acquisition [Line Items]      
Business acquisition, consideration amount $ 76,600    
Business acquisition, deferred payment $ 10,000    
Business acquisition, deferred payment term 2 years    
Business acquisition, additional variable payment term 10 years    
Business combination, accrued for deferred and variable payments $ 1,300    
Stand-Alone Pre-Owned Vehicle Store [Member] | Maximum [Member]      
Business Acquisition [Line Items]      
Business acquisition, additional variable payment 80,000    
Stand-Alone Pre-Owned Vehicle Store [Member] | Maximum [Member] | Employee Termination [Member]      
Business Acquisition [Line Items]      
Business acquisition, additional variable payment 80,000    
Stand-Alone Pre-Owned Vehicle Store [Member] | Pre-Owned Stores Segment [Member]      
Business Acquisition [Line Items]      
Goodwill acquired related to acquisition $ 60,000    
Stand-Alone Pre-Owned Vehicle Store And Related Real Estate [Member]      
Business Acquisition [Line Items]      
Business acquisition, consideration amount   $ 15,900  
Number of businesses acquired | Business   3