Annual report pursuant to Section 13 and 15(d)

Nature Of Operations And Accounting Policies (Estimated Useful life Of Major Assets) (Details)

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Nature Of Operations And Accounting Policies (Estimated Useful life Of Major Assets) (Details)
12 Months Ended
Dec. 31, 2019
Petroleum and chemical carriers - U.S.-flag  
Property, Plant and Equipment [Line Items]  
Estimated useful life (in years) 25 years
Bulk carriers - U.S.-flag  
Property, Plant and Equipment [Line Items]  
Estimated useful life (in years) 25 years
Harbor and offshore tugs  
Property, Plant and Equipment [Line Items]  
Estimated useful life (in years) 25 years
Ocean liquid tank barges  
Property, Plant and Equipment [Line Items]  
Estimated useful life (in years) 25 years
Short-sea container/RORO vessels  
Property, Plant and Equipment [Line Items]  
Estimated useful life (in years) 20 years
Inland river dry-cargo and specialty barges  
Property, Plant and Equipment [Line Items]  
Estimated useful life (in years) 20 years
Inland river liquid tank barges  
Property, Plant and Equipment [Line Items]  
Estimated useful life (in years) 25 years
Inland river towboats and harbor boats  
Property, Plant and Equipment [Line Items]  
Estimated useful life (in years) 25 years
Terminal and fleeting facilities  
Property, Plant and Equipment [Line Items]  
Estimated useful life (in years) 20 years