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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Jun. 30, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Accounting Policies [Line Items]        
General And Administrative Expenses Cost Of Goods Sold Depreciation   $ 16,700 $ 15,900 $ 16,000
Capital Leases, Balance Sheet, Assets by Major Class, Net   3,200 4,300  
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation   1,400 1,900  
Amortization Of Intangible Assets   17,041 19,940 21,259
Estimated amortization expense for 2018   20,400    
Estimated amortization expense for 2019   21,600    
Estimated amortization expense for 2020   23,100    
Estimated amortization expense for 2021   24,400    
Estimated amortization expense for 2022   19,500    
Imparment of goodwill   0 1,663 1,087
Capitalized Computer Software, Net   7,300 5,400  
Research and Development Expense   3,900 6,400 4,800
Capitalized Computer Software, Amortization   1,300 1,000 700
Goodwill   317,464 148,367 149,718
Commercial Trailer Products        
Accounting Policies [Line Items]        
Imparment of goodwill $ 1,700      
Goodwill   2,700    
Final Mile Products [Member]        
Accounting Policies [Line Items]        
Goodwill   169,200    
Diversified Products [Member]        
Accounting Policies [Line Items]        
Goodwill   145,600    
Used Trailers        
Accounting Policies [Line Items]        
Accounts Payable, Trade   3,200    
Property, Plant and Equipment, Additions   $ 9,500 $ 4,600 $ 12,800
Building and Building Improvements        
Accounting Policies [Line Items]        
Property, Plant and Equipment, Useful Life   33 years