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 ($)
 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Long-term Contracts or Programs Disclosure [Line Items]      
Contracts in progress $ 42,810,000   $ 26,829,000
Advance billings on contracts 4,367,000   3,977,000
Accrued contract losses 1,982,000   $ 387,000
Change in estimated costs 12,700,000    
Loss related to disputed change orders   $ 488,000  
Project, Approved Scope, Unapproved Price      
Long-term Contracts or Programs Disclosure [Line Items]      
Revenue 0    
Two Major Customers | Costs in Excess of Billings | Customer Concentration Risk      
Long-term Contracts or Programs Disclosure [Line Items]      
Contracts in progress 31,700,000    
Two Major Customers | Billings in Excess of Costs | Customer Concentration Risk      
Long-term Contracts or Programs Disclosure [Line Items]      
Customer advances $ 3,200,000