Annual report pursuant to Section 13 and 15(d)

Acquisitions, Goodwill and Other Long-Lived Assets Carrying Value of Goodwill (Details)

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Acquisitions, Goodwill and Other Long-Lived Assets Carrying Value of Goodwill (Details)
$ in Thousands
 6 Months Ended 12 Months Ended
Jun. 30, 2019
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Goodwill [Line Items]        
Number of Reportable Segments 5      
Business Acquisition, Goodwill, Expected Tax Deductible Amount   $ 141,961    
Goodwill, Gross   253,744 $ 231,731  
Accumulated impairment loss   (32,639) (32,639)  
Goodwill, Net   221,105 199,092  
Amortization expense of acquired intangible assets   $ 11,213 9,138 $ 10,193
Customer Relationships [Member]        
Goodwill [Line Items]        
Finite-Lived Intangible Asset, Useful Life   15 years 4 months 24 days    
Noncompete Agreements [Member]        
Goodwill [Line Items]        
Finite-Lived Intangible Asset, Useful Life   4 years 8 months 12 days    
Trade Names [Member]        
Goodwill [Line Items]        
Finite-Lived Intangible Asset, Useful Life   4 years    
Expedited LTL [Member]        
Goodwill [Line Items]        
Goodwill, Gross   $ 97,593 97,593  
Truckload Premium Services [Member]        
Goodwill [Line Items]        
Goodwill, Gross   45,164 45,164  
Accumulated impairment loss   (25,686) (25,686)  
Final Mile [Member]        
Goodwill [Line Items]        
Goodwill, Gross   19,963    
Intermodal [Member]        
Goodwill [Line Items]        
Goodwill, Gross   78,665 76,615  
Pool Distribution [Member]        
Goodwill [Line Items]        
Goodwill, Gross   12,359 12,359  
Accumulated impairment loss   $ (6,953) $ (6,953)  
Atlantic [Member] | Customer Relationships [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   15 years    
Atlantic [Member] | Noncompete Agreements [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   5 years    
KCL [Member] | Customer Relationships [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   15 years    
KCL [Member] | Noncompete Agreements [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   2 years    
MMT [Member] | Customer Relationships [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   15 years    
MMT [Member] | Noncompete Agreements [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   4 years    
Southwest Freight Distributors [Member] | Customer Relationships [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   10 years    
Southwest Freight Distributors [Member] | Noncompete Agreements [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   3 years    
FSA [Member]        
Goodwill [Line Items]        
Goodwill, Acquired During Period   $ 19,963    
FSA [Member] | Customer Relationships [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   15 years    
FSA [Member] | Noncompete Agreements [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   5 years    
OST [Member]        
Goodwill [Line Items]        
Goodwill, Acquired During Period   $ 2,050    
OST [Member] | Customer Relationships [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   10 years    
OST [Member] | Noncompete Agreements [Member]        
Goodwill [Line Items]        
Weighted average useful lives of acquired intangible assets   3 years