Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Accounts Receivable (Details)

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Summary of Significant Accounting Policies - Accounts Receivable (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Allowance for Doubtful Accounts Receivable [Roll Forward]        
Allowance for doubtful accounts, beginning of period $ 3,729 $ 7,836 $ 3,729 $ 2,851
Charges to costs and expenses   81 4,332 1,451
Account write-offs and other   (4,602) (225) (573)
Allowance for doubtful accounts, end of period   3,315 7,836 3,729
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Accounts receivable retainage reserve   $ 0 887 $ 1,282
Minimum        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Accounts receivable retainage   5.00%    
Maximum        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Accounts receivable retainage   10.00%    
Operating Segments | Canada        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Interest and debt expense   $ 1,934 1,934  
Accounts receivable        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Allowance for doubtful accounts receivable, period increase     2,394  
Interest and debt expense     1,655  
Costs in Excess of Billings        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Allowance for doubtful accounts receivable, period increase 476      
Construction in Progress, Gross        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Allowance for doubtful accounts receivable, period increase $ 325      
Contract Receivable Retainage        
Accounts, Notes, Loans and Financing Receivable [Line Items]        
Interest and debt expense     $ 279