Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation and Accounting Policies Property and Equipment (Details)

v3.8.0.1
Basis of Presentation and Accounting Policies Property and Equipment (Details)
$ in Millions
3 Months Ended
Mar. 31, 2018
USD ($)
Property, Plant and Equipment [Line Items]  
Capitalized Interest Costs, Including Allowance for Funds Used During Construction $ 0.2
U.S.-flag Petroleum and Chemical Carrier [Member]  
Property, Plant and Equipment [Line Items]  
Property, Plant and Equipment, Useful Life 25 years
Harbor and Offshore Tugs [Member]  
Property, Plant and Equipment [Line Items]  
Property, Plant and Equipment, Useful Life 25 years
Ocean Liquid Tank Barge [Member]  
Property, Plant and Equipment [Line Items]  
Property, Plant and Equipment, Useful Life 25 years
Short-sea Container/RORO Vessels [Member]  
Property, Plant and Equipment [Line Items]  
Property, Plant and Equipment, Useful Life 20 years
U.S.-flag dry-bulk carrier [Member]  
Property, Plant and Equipment [Line Items]  
Property, Plant and Equipment, Useful Life 25 years
Inland River Dry Cargo and Deck Barges [Member]  
Property, Plant and Equipment [Line Items]  
Property, Plant and Equipment, Useful Life 20 years
Inland River Liquid Tank Barges [Member]  
Property, Plant and Equipment [Line Items]  
Property, Plant and Equipment, Useful Life 25 years
Inland River Towboats [Member]  
Property, Plant and Equipment [Line Items]  
Property, Plant and Equipment, Useful Life 25 years
Terminal And Manufacturing Facilities [Member]  
Property, Plant and Equipment [Line Items]  
Property, Plant and Equipment, Useful Life 20 years