Quarterly report pursuant to Section 13 or 15(d)

Assets Held for Sale - Narrative (Details)

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Assets Held for Sale - Narrative (Details)
 3 Months Ended 7 Months Ended
Apr. 20, 2018
USD ($)
Jan. 03, 2018
USD ($)
Jun. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
T
Dec. 31, 2017
USD ($)
Jun. 30, 2017
USD ($)
drydock
Mar. 31, 2017
USD ($)
Mar. 31, 2018
USD ($)
Long Lived Assets Held-for-sale [Line Items]                
Number of drydocks sold | drydock           2    
Disposal Group, Held-for-sale, Not Discontinued Operations                
Long Lived Assets Held-for-sale [Line Items]                
Property, plant and equipment held for sale       $ 98,386,000       $ 98,386,000
Disposal Group, Held-for-sale, Not Discontinued Operations | South Texas Fabrication Yards                
Long Lived Assets Held-for-sale [Line Items]                
Proceeds from sale of PP&E   $ 750,000            
Insurance deductible, percent       3.00%       3.00%
Estimated insurance recoveries       $ 17,800,000       $ 17,800,000
Insurance initial payment       2,200,000       8,200,000
Clean-up and repair related costs due to Hurricane Harvey               1,600,000
Accrual for future repairs         $ 1,500,000      
Disposal Group, Held-for-sale, Not Discontinued Operations | South Texas Fabrication Yards | Maximum                
Long Lived Assets Held-for-sale [Line Items]                
Insurance coverage       25,000,000       25,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations | South Texas Fabrication Yards | Minimum                
Long Lived Assets Held-for-sale [Line Items]                
Insurance deductible, value         500,000      
Disposal Group, Held-for-sale, Not Discontinued Operations | Texas North Yard                
Long Lived Assets Held-for-sale [Line Items]                
Impairment of real estate       5,100,000        
Impairment of equipment       750,000        
Property, plant and equipment held for sale       46,600,000       46,600,000
Disposal Group, Held-for-sale, Not Discontinued Operations | Shipyard Division Assets                
Long Lived Assets Held-for-sale [Line Items]                
Impairment of assets held for sale         $ 600,000   $ 389,000  
Property, plant and equipment held for sale       $ 1,889,000       1,889,000
Disposal Group, Held-for-sale, Not Discontinued Operations | Subsequent Event | South Texas Fabrication Yards                
Long Lived Assets Held-for-sale [Line Items]                
Sale of PP&E $ 55,000,000              
Cost of PP&E sales 1,500,000              
Proceeds from sale of PP&E 52,700,000              
Gain (loss) on sale of assets     $ 3,800,000          
Decrease in assets held for sale $ 49,900,000              
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Shipyard Division Assets                
Long Lived Assets Held-for-sale [Line Items]                
Sale of PP&E           $ 2,000,000    
Gain (loss) on sale of assets           $ (259,000)    
Drydock, number of tons | T       2,500        
Property, plant and equipment held for sale       $ 1,900,000       $ 1,900,000