Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Details)

v3.10.0.1
Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Jan. 01, 2018
Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]            
Contract work in process     $ 3,300      
Contract Assets         $ 2,082  
Percentage of dealership that is accounted for under the equity method 50.00%   50.00%     50.00%
Effective tax rate from continuing operations 32.40% 39.30% 29.70% 39.80%    
Effective Income Tax Rate Reconciliation, Disposition of Asset, Amount $ 600          
Income benefit $ (8,222) $ (7,956) $ (6,380) $ (8,128)    
Discrete benefit related to vested or exercised stock compensation     900      
Tax expense for uncertain tax positions     $ 200      
Minimum            
Schedule of Equity Method Investments [Line Items]            
Expected annual effective tax rate in future periods     26.00%      
Maximum            
Schedule of Equity Method Investments [Line Items]            
Expected annual effective tax rate in future periods     28.00%      
Dealership            
Schedule of Equity Method Investments [Line Items]            
Percentage of dealership that is accounted for under the equity method 50.00%   50.00%      
ASU 2014-09 | Finance, insurance and other, net            
Schedule of Equity Method Investments [Line Items]            
Contract Assets $ 6,000   $ 6,000      
ASU 2016-09            
Schedule of Equity Method Investments [Line Items]            
Income benefit   $ 200   $ 500