Quarterly report pursuant to Section 13 or 15(d)

Equipment Acquisitions, Dispositions and Depreciation and Impairment Policies (Narrative) (Details)

v3.5.0.2
Equipment Acquisitions, Dispositions and Depreciation and Impairment Policies (Narrative) (Details)
$ in Thousands
9 Months Ended
Sep. 30, 2016
USD ($)
equipment
Sep. 30, 2015
USD ($)
Property, Plant and Equipment [Line Items]    
Payments to Acquire Property, Plant, and Equipment | $ $ 294,115 $ 227,244
Sales Price Of Equipment | $ 156,100  
Proceeds from disposition of property and equipment | $ 146,195 95,396
Proceeds from Issuance of Secured Debt | $ 8,000  
Gain (Loss) on Disposition of Property Plant Equipment | $ 11,400  
Increase (Decrease) in Deferred Charges | $ (9,003) (5,971)
Amortization Of Deferred Gains Included In Gains On Asset Dispositions And Impairments, Net | $ $ 2,850 1,667
Offshore Support Vessels Fast Support [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Delivered 12  
Offshore Support Vessels Supply [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Delivered 1  
Number Of Equipments Sold (1)  
Wind Farm Utility Vessel [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Delivered 2  
Inland River Towboat [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Delivered 2  
Number Of Equipments Sold (14)  
Inland River Dry Cargo Barges [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Delivered 12  
U.S.-flag Product Tankers [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Delivered 2  
Sale Leaseback Transaction, Net Proceeds, Investing Activities | $ $ 61,000  
Sale Leaseback Transaction, Lease Terms 76  
U.S.-flag Harbor Tugs [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipment Acquired 1  
Number Of Equipments Sold (1)  
Noncash or Part Noncash Divestiture, Amount of Consideration Received | $ $ 2,000  
Offshore Support Vessels Mini Supply [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Sold (1)  
Offshore Support Vessels Standby Safety [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Sold (4)  
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]    
Property, Plant and Equipment [Line Items]    
Proceeds from disposition of property and equipment | $ $ 146,100  
Inland River Liquid Tank Barges - 30,000 Barrel [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Sold (20)  
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]    
Property, Plant and Equipment [Line Items]    
Proceeds from disposition of property and equipment | $ $ 100  
Gain (Loss) on Asset Dispositions and Impairments, Net [Member]    
Property, Plant and Equipment [Line Items]    
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property | $ 2,400  
Amortization Of Deferred Gains Included In Gains On Asset Dispositions And Impairments, Net | $ $ 1,852 $ 5,437
Property Subject to Operating Lease [Member] | U.S.-flag Product Tankers [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Sold (1)  
Property Subject to Operating Lease [Member] | Inland River Liquid Tank Barges - 30,000 Barrel [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipments Removed from Service 8  
Construction in Progress [Member] | Inland River Towboat [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipments Removed from Service 1