Annual report pursuant to Section 13 and 15(d)

Summary of Quarterly Financial Data (Unaudited) - Additional Information (Detail)

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Summary of Quarterly Financial Data (Unaudited) - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Mar. 31, 2016
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Condensed Unaudited Quarterly Financial Data [Line Items]                      
Tax benefit related to deferred income tax impact of change in U.S. federal tax income rate $ (28,400)               $ (28,400)    
U.S. statutory federal income tax rate                 35.00% 35.00% 35.00%
Pre-tax benefit related to storm damage and other accrual adjustments 1,400       $ 400 $ 2,300          
Pre-tax gain (loss) on disposal                 $ 11,188 $ (47) $ 2,748
Asset impairment charges 6,100 $ 200 $ 2,600 $ 500 1,800 6,100 $ 6,000   9,394 $ 8,063 $ 17,955
Pre-tax legal and other charges 1,500                    
Pre-tax charges against to natural damages   3,000 4,600 2,400              
Pre-tax charges related to legal and other accrual adjustments   1,000                  
Pre-tax legal accruals and settlements     1,000                
Lease exit expense     $ 1,000           2,200    
Pre-tax charge related to the extinguishment of debt                 $ (14,607)    
Net benefit from legal settlements       1,100              
Pre-tax benefit related to manufacturer legal settlement         14,800            
Pre-tax benefit (charges) related to lease exit accrual adjustments in discontinued operations         $ (500) $ (1,000) $ 500        
7.0% Senior Subordinated Notes Expired [Member]                      
Condensed Unaudited Quarterly Financial Data [Line Items]                      
Pre-tax charge related to the extinguishment of debt       $ (15,300)              
Stated interest rate on debt agreement       7.00%              
Franchised Dealerships Segment [Member]                      
Condensed Unaudited Quarterly Financial Data [Line Items]                      
Pre-tax gain (loss) on disposal $ 1,500 $ 8,500                  
Scenario, Forecast [Member]                      
Condensed Unaudited Quarterly Financial Data [Line Items]                      
U.S. statutory federal income tax rate               21.00%