Annual report pursuant to Section 13 and 15(d)

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

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Equipment Acquisitions And Dispositions (Major Equipment Dispositions) (Details) - equipment
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Petroleum and chemical carriers - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 0 1 1
Harbor tugs - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 0 1 0
Short-sea container/RORO - Foreign-flag      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 1 0 0
Inland river dry-cargo barges      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 0 32 50
Inland river specialty barges      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 0 2 2
Inland river towboats      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 0 0 2