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Long-Term Debt and Financing Arrangements - Additional Information (Detail)
 12 Months Ended
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Dec. 31, 2011
Chassis
Line Of Credit Facility [Line Items]        
Maximum unsecured borrowing capacity     $ 50,000,000  
Line of credit, expiration date   Dec. 31, 2018    
Number of chassis leased | Chassis       3,126
Chassis, lease agreement period (years)       10 years
Capital lease interest paid $ 700,000 $ 800,000 $ 900,000  
Standby Letters of Credit [Member]        
Line Of Credit Facility [Line Items]        
Outstanding letters of credit $ 8,200,000      
Letters of credit expiration, years 2016      
Revolving Line of Credit Facility [Member] | Bank Revolving Line of Credit [Member]        
Line Of Credit Facility [Line Items]        
Unused and available borrowings under bank revolving line of credit $ 41,800,000 $ 43,900,000    
Minimum [Member]        
Line Of Credit Facility [Line Items]        
Commitment fee charged on the unused line of credit     0.10%  
Interest coverage ratio     2.00%  
Maximum [Member]        
Line Of Credit Facility [Line Items]        
Commitment fee charged on the unused line of credit     0.25%  
Total leverage ratio     3.00%  
LIBOR rate [Member] | Minimum [Member]        
Line Of Credit Facility [Line Items]        
Interest rate under the Credit Agreement     1.00%  
LIBOR rate [Member] | Maximum [Member]        
Line Of Credit Facility [Line Items]        
Interest rate under the Credit Agreement     1.75%  
Prime Rate [Member]        
Line Of Credit Facility [Line Items]        
Interest rate under the Credit Agreement     0.75%