Annual report pursuant to Section 13 and 15(d)

Equipment Acquisitions And Dispositions (Narrative) (Details)

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Equipment Acquisitions And Dispositions (Narrative) (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2017
USD ($)
equipment
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Business Acquisition [Line Items]      
Sales Price Of Equipment $ 164,800 $ 153,000 $ 81,500
Proceeds from Sale of Property, Plant, and Equipment 164,789 143,028 79,762
Proceeds from Issuance of Secured Debt   8,000 1,700
Noncash or Part Noncash Divestiture, Amount of Consideration Received   2,000  
Gain (Loss) on Disposition of Property Plant Equipment 23,300 11,300 17,400
Increase (Decrease) in Deferred Charges $ (13,300) 9,000 6,000
Sale Leaseback Transaction, Net Proceeds, Investing Activities   61,000 35,300
Sale Leaseback Transaction, Deferred Gain, Net   $ 8,200 $ 4,200
U.S.-flag Petroleum and Chemical Carriers [Member]      
Business Acquisition [Line Items]      
Sale Leaseback Transaction, Description of Asset(s) 1 1  
Sale Leaseback Transaction, Net Proceeds, Investing Activities $ 134,900    
Inland River Dry Cargo Barges [Member]      
Business Acquisition [Line Items]      
Sale Leaseback Transaction, Description of Asset(s) 50    
Sale Leaseback Transaction, Net Proceeds, Investing Activities $ 12,500    
Inland River Specialty Barges [Member]      
Business Acquisition [Line Items]      
Number of Equipments Removed from Service | equipment 1    
Inland River Towboats [Member]      
Business Acquisition [Line Items]      
Sale Leaseback Transaction, Description of Asset(s)     4
Maximum [Member]      
Business Acquisition [Line Items]      
Sale Leaseback Transaction, Lease Terms   76 84
Maximum [Member] | U.S.-flag Petroleum and Chemical Carriers [Member]      
Business Acquisition [Line Items]      
Sale Leaseback Transaction, Lease Terms 104    
Maximum [Member] | Inland River Dry Cargo Barges [Member]      
Business Acquisition [Line Items]      
Sale Leaseback Transaction, Lease Terms 84    
Gain (Loss) on Asset Dispositions and Impairments, Net [Member]      
Business Acquisition [Line Items]      
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property $ 10,000 $ 2,300 $ 11,400
Amortization of Deferred Charges 2,300 $ 2,400 $ 3,200
Gain (Loss) on Asset Dispositions and Impairments, Net [Member] | Inland River Specialty Barges [Member]      
Business Acquisition [Line Items]      
Gain (Loss) on Disposition of Property Plant Equipment $ (300)