Quarterly report pursuant to Section 13 or 15(d)

Revenue and Contract Costs - Narrative (Details)

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Revenue and Contract Costs - Narrative (Details) - USD ($)
 3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2017
Jun. 30, 2016
Dec. 31, 2016
Long-term Contracts or Programs Disclosure [Line Items]        
Contracts in progress $ 31,643,000 $ 31,643,000   $ 26,829,000
Advance billings on contracts 8,642,000 8,642,000   3,977,000
Accrued contract losses 3,514,000 3,514,000   $ 387,000
Change in estimated costs 10,200,000      
Loss related to disputed change orders     $ 488,000  
Project, Approved Scope, Unapproved Price        
Long-term Contracts or Programs Disclosure [Line Items]        
Revenue   0    
One Major Customer | Customer Concentration Risk | Costs in Excess of Billings        
Long-term Contracts or Programs Disclosure [Line Items]        
Contracts in progress 28,100,000 28,100,000    
Two Major Customers | Customer Concentration Risk | Billings in Excess of Costs        
Long-term Contracts or Programs Disclosure [Line Items]        
Customer advances $ 7,800,000 $ 7,800,000