Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies (Details)

v3.8.0.1
Commitments and Contingencies (Details) - USD ($)
 6 Months Ended 9 Months Ended
Mar. 10, 2017
Dec. 31, 2015
Sep. 30, 2017
Dec. 31, 2016
Loss Contingencies [Line Items]        
Contract receivable     $ 25,513,000 $ 20,169,000
Contracts in progress     42,810,000 $ 26,829,000
Change in estimated costs     12,700,000  
Minimum        
Loss Contingencies [Line Items]        
Possible late delivery penalty per contract     0  
Maximum        
Loss Contingencies [Line Items]        
Possible late delivery penalty per contract     5,600,000  
Customer of Shipyard        
Loss Contingencies [Line Items]        
Loss contingency, damages sought by plaintiff $ 84,800,000      
Customer of Shipyard | Contract Receivable        
Loss Contingencies [Line Items]        
Contract receivable     4,600,000  
Contracts in progress     $ 4,900,000  
Large Deepwater Project, Recently Delivered        
Loss Contingencies [Line Items]        
Contract losses   $ 24,500,000