XML 56 R43.htm IDEA: XBRL DOCUMENT v3.6.0.2
Summary of Significant Accounting Policies - Additional Information (Detail)
3 Months Ended 12 Months Ended
Sep. 30, 2016
USD ($)
Dec. 31, 2016
USD ($)
Company
Segment
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Accounting Policies [Line Items]        
Proceeds from sale of marketable securities   $ 900,000 $ 400,000  
Cost on sale of marketable securities   500,000 100,000  
Realized gain on sale of marketable securities   400,000 300,000  
Equity securities at book value   3,500,000    
Temporary impairment loss of equity securities   $ 600,000    
Number of investments in publicly traded companies | Company   27    
Depreciation expense   $ 29,200,000 25,800,000 $ 23,100,000
Weighted average amortization period   12 years    
Amounts recorded for amortization expense   $ 7,500,000 9,200,000 9,900,000
Goodwill impairment loss recognized $ 0      
Goodwill   $ 74,484,000 74,484,000  
Deferred compensation bonus annual installments   5 years    
Fuel surcharges   $ 50,900,000 75,700,000 $ 119,700,000
Number of reportable segments | Segment   2    
Prepaid expenses and other   $ 17,374,000 17,858,000  
Other noncurrent assets   4,892,000 3,894,000  
Equity Securities, Gross unrealized holding gains   4,780,000 3,958,000  
Equity Securities, Gross unrealized holding (losses)   (589,000) (1,141,000)  
Disclose of operating lease obligations   $ 72,100,000    
Reclassification Adjustment [Member]        
Accounting Policies [Line Items]        
Prepaid expenses and other     300,000  
Other noncurrent assets     $ 1,200,000  
Customer Concentration Risk [Member] | Sales Revenue, Net [Member]        
Accounting Policies [Line Items]        
Percentage of revenues from major customers   42.50% 37.30% 36.50%
General Motors [Member] | Customer Concentration Risk [Member] | Sales Revenue, Net [Member]        
Accounting Policies [Line Items]        
Percentage of revenues from major customers   17.90% 11.40% 9.70%
Top Ten Customers [Member] | Customer Concentration Risk [Member] | Sales Revenue, Net [Member]        
Accounting Policies [Line Items]        
Percentage of revenues from major customers   40.90%    
Transportation [Member]        
Accounting Policies [Line Items]        
Goodwill   $ 18,200,000 $ 18,200,000  
Logistics [Member]        
Accounting Policies [Line Items]        
Goodwill   $ 56,300,000 $ 56,300,000  
Customer contracts [Member]        
Accounting Policies [Line Items]        
Weighted average amortization period   3 years    
Agent and customer relationships [Member]        
Accounting Policies [Line Items]        
Weighted average amortization period   15 years    
Minimum [Member]        
Accounting Policies [Line Items]        
Estimated useful lives   3 years    
Maximum [Member]        
Accounting Policies [Line Items]        
Estimated useful lives   19 years