Quarterly report pursuant to Section 13 or 15(d)

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

v3.7.0.1
Equipment Acquisitions, Dispositions and Depreciation and Impairment Policies (Narrative) (Details)
$ in Thousands
6 Months Ended
Jun. 30, 2017
USD ($)
equipment
Jun. 30, 2016
USD ($)
Property, Plant and Equipment [Line Items]    
Payments to Acquire Property, Plant, and Equipment $ 28,803 $ 45,840
Sales Price Of Equipment 10,000  
Proceeds from disposition of property and equipment $ 9,549 $ 3,139
Offshore Support Vessels Fast Support [Member]    
Property, Plant and Equipment [Line Items]    
Number of Equipment Acquired | equipment 4  
Liftboats [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Sold | equipment (2)  
Offshore Support Vessels Mini Supply [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Sold | equipment (1)  
Offshore Support Vessels [Member]    
Property, Plant and Equipment [Line Items]    
Number Of Equipments Sold | equipment (4)  
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]    
Property, Plant and Equipment [Line Items]    
Proceeds from disposition of property and equipment $ 9,500  
Gain (Loss) on Asset Dispositions and Impairments, Net [Member]    
Property, Plant and Equipment [Line Items]    
Gain (Loss) on Disposition of Property Plant Equipment 4,200  
Fair Value Hedging [Member]    
Property, Plant and Equipment [Line Items]    
Payments to Acquire Property, Plant, and Equipment 29,100  
Other Current Liabilities [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]    
Property, Plant and Equipment [Line Items]    
Proceeds from disposition of property and equipment $ 500