Annual report pursuant to Section 13 and 15(d)

Contracts Receivable and Retainage - Amounts Due on Contracts (Details)

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Contracts Receivable and Retainage - Amounts Due on Contracts (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Long-term Contracts or Programs Disclosure [Line Items]    
Current receivables $ 28,466 $ 20,169
Total contracts receivable 30,214 21,173
Less allowance for doubtful accounts 1,748 1,004
Net contracts receivable 28,466 20,169
Completed Contracts    
Long-term Contracts or Programs Disclosure [Line Items]    
Current receivables 10,246 6,812
Contracts In Progress    
Long-term Contracts or Programs Disclosure [Line Items]    
Current receivables 15,513 14,248
Retainage 4,455 113
Top 2 Customers    
Long-term Contracts or Programs Disclosure [Line Items]    
Current receivables $ 15,600  
Percentage of contract receivable 55.10%  
Top 3 Customers    
Long-term Contracts or Programs Disclosure [Line Items]    
Current receivables   $ 8,600
Percentage of contract receivable   42.70%