Annual report pursuant to Section 13 and 15(d)

Equipment Acquisitions And Dispositions (Major Equipment Deliveries) (Details)

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Equipment Acquisitions And Dispositions (Major Equipment Deliveries) (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2017
USD ($)
equipment
Vessel
Dec. 31, 2016
USD ($)
equipment
Dec. 31, 2015
USD ($)
equipment
Payments to Acquire Property, Plant, and Equipment | $ $ 114,595 $ 252,806 $ 203,453
U.S.-flag Petroleum and Chemical Carriers [Member]      
Number Of Equipments Acquired 3 3 0
U.S.-flag Harbor Tugs [Member]      
Number Of Equipments Acquired 1 1 0
Foreign-flag Harbor Tugs [Member]      
Number Of Equipments Delivered 2 0 0
Inland River Dry Cargo Barges [Member]      
Number Of Equipments Acquired 0 46 0
Inland River Liquid Tank Barges [Member]      
Number Of Equipments Acquired 2 0 8
Inland River Specialty Barges [Member]      
Number Of Equipments Acquired 0 0 4
Inland River Towboats [Member]      
Number Of Equipments Acquired 3 2 9
ISH [Member] | U.S.-flag Dry bulk Carrier [Member]      
Number Of Equipments Acquired 2    
Central Contracting & Marine, Inc. [Member] | Inland River Harbor Boats [Member]      
Number Of Equipments Acquired 5 5  
SeaJon II [Member] | U.S.-flag Harbor Tugs [Member]      
Number Of Equipments Acquired 1