Annual report pursuant to Section 13 and 15(d)

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

v3.20.4
Equipment Acquisitions And Dispositions (Major Equipment Dispositions) (Details) - equipment
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Petroleum and chemical carriers - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 0 0 1
Bulk carriers - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 1 0 0
Harbor tugs - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 0 0 1
Offshore tug - U.S.-flag      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 1 0 0
Short-sea container/RORO vessels - Foreign-flag      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 0 1 0
Inland river dry-cargo barges      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 39 0 32
Inland river specialty barges      
Property, Plant and Equipment [Line Items]      
Number of equipment disposed 0 0 2