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 ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2016
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]        
Allowance for doubtful accounts, beginning of period $ 3,729,000 $ 3,315,000 $ 7,836,000 $ 3,729,000
Charges to costs and expenses   610,000 81,000 4,332,000
Account write-offs and other   (1,160,000) (4,602,000) (225,000)
Allowance for doubtful accounts, end of period   2,765,000 3,315,000 7,836,000
Accounts receivable retainage reserve   $ 0 $ 0  
Minimum        
Allowance for Doubtful Accounts Receivable [Roll Forward]        
Accounts receivable retainage   5.00%    
Maximum        
Allowance for Doubtful Accounts Receivable [Roll Forward]        
Accounts receivable retainage   10.00%    
Operating Segments | Canada        
Allowance for Doubtful Accounts Receivable [Roll Forward]        
Interest and debt expense       1,934,000
Accounts receivable        
Allowance for Doubtful Accounts Receivable [Roll Forward]        
Allowance for doubtful accounts receivable, period increase       2,394,000
Interest and debt expense       1,655,000
Costs in Excess of Billings        
Allowance for Doubtful Accounts Receivable [Roll Forward]        
Allowance for doubtful accounts receivable, period increase 476,000      
Construction in Progress, Gross        
Allowance for Doubtful Accounts Receivable [Roll Forward]        
Allowance for doubtful accounts receivable, period increase $ 325,000      
Contract Receivable Retainage        
Allowance for Doubtful Accounts Receivable [Roll Forward]        
Interest and debt expense       $ 279,000