v3.8.0.1
Equipment Acquisitions, Dispositions and Depreciation and Impairment Policies (Narrative) (Details)
$ in Thousands
 9 Months Ended
Sep. 30, 2017
USD ($)
equipment
Sep. 30, 2016
USD ($)
Property, Plant and Equipment [Line Items]    
Payments to Acquire Property, Plant, and Equipment | $ $ 99,306 $ 207,825
Sales Price Of Equipment | $ 27,600  
Gain (Loss) on Disposition of Property Plant Equipment | $ 17,600  
Increase (Decrease) in Deferred Charges | $ 7,720 9,003
Sale Leaseback Transaction, Net Proceeds, Investing Activities | $ 12,500  
Amortization Of Deferred Gains Included In Gains On Asset Dispositions And Impairments, Net | $ $ 0 1,697
Inland River Liquid Tank Barges [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipment Acquired | equipment 2  
Inland River Towboat [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipment Acquired | equipment 3  
Number Of Equipments Sold | equipment 2  
U.S. Flag Articulated Tug-Barge [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipment Acquired | equipment 1  
U.S.-flag Product Tankers [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipment Acquired | equipment 1  
U.S.-flag Harbor Tugs [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipment Acquired | equipment 1  
Foreign-flag Harbor Tugs [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipment Acquired | equipment 2  
Inland River Dry Cargo Barges [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Sold | equipment 50  
Sale Leaseback Transaction, Description of Asset(s) 50  
Sale Leaseback Transaction, Lease Terms 84  
Inland River Specialty Barges [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipments Removed from Service | equipment (1)  
Gain (Loss) on Asset Dispositions and Impairments, Net [Member]    
Property, Plant and Equipment [Line Items]    
Gain (Loss) on Disposition of Property Plant Equipment | $ $ 9,900  
Amortization Of Deferred Gains Included In Gains On Asset Dispositions And Impairments, Net | $ 1,764 $ 1,816
Gain (Loss) on Asset Dispositions and Impairments, Net [Member] | Inland River Specialty Barges [Member]    
Property, Plant and Equipment [Line Items]    
Gain (Loss) on Disposition of Property Plant Equipment | $ $ (400)