Annual report pursuant to Section 13 and 15(d)

Operating Leases (Details)

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Operating Leases (Details) - equipment
12 Months Ended
Dec. 31, 2019
Dec. 31, 2017
Petroleum and Chemical Carriers - U.S.-flag    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 2  
Sale Leaseback Transaction, Lease Terms   104 months
Petroleum and Chemical Carriers - U.S.-flag | Minimum    
Operating Leases [Line Items]    
Sale Leaseback Transaction, Lease Terms 33  
Petroleum and Chemical Carriers - U.S.-flag | Maximum    
Operating Leases [Line Items]    
Sale Leaseback Transaction, Lease Terms 80  
Harbor Tugs - U.S.-flag    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 4  
Pure Car/Truck Carriers - U.S.-flag    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 4  
Inland River Dry-Cargo Barges    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 50  
Sale Leaseback Transaction, Lease Terms   84 months
Inland River Towboats    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 4  
Inland River Harbor Boats    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 6  
Other Equipment | Minimum    
Operating Leases [Line Items]    
Lessee, Operating Lease, Term of Contract 4 months  
Other Equipment | Maximum    
Operating Leases [Line Items]    
Lessee, Operating Lease, Term of Contract 195 months  
Bareboat Chartered, Petroleum and Chemical Carriers - U.S.-flag    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 4  
Bareboat Chartered, Ocean Liquid Tank Barges - U.S.-flag    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 5  
Bareboat Chartered, Harbor Tugs - Foreign-flag    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 6  
Time Chartered, Petroleum and Chemical Carriers - U.S.-flag    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 4  
Time Chartered, PCTCs - U.S.-flag    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 4  
Time Chartered, Inland River Towboats    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 8  
Time Chartered, Offshore Tug - U.S.-flag    
Operating Leases [Line Items]    
Equipment Subject to Operating Lease, Number of Units 1