Annual report pursuant to Section 13 and 15(d)

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

v3.8.0.1
Equipment Acquisitions And Dispositions (Major Equipment Dispositions) (Details) - equipment
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
U.S.-flag Petroleum and Chemical Carriers [Member]      
Number of Equipments Removed from Service 1 1 0
U.S.-flag Harbor Tugs [Member]      
Number of Equipments Removed from Service 0 2 0
Inland River Dry Cargo Barges [Member]      
Number of Equipments Removed from Service 50 0 0
Inland River Liquid Tank Barges [Member]      
Number of Equipments Removed from Service 0 19 35
Inland River Specialty Barges [Member]      
Number of Equipments Removed from Service 2 0 0
Inland River Specialty Barges [Member]      
Number of Equipments Removed from Service 0 0 12
Inland River Towboats [Member]      
Number of Equipments Removed from Service 2 14 4