Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Accounts Receivable (Details)

v3.8.0.1
Summary of Significant Accounting Policies - Accounts Receivable (Details) - USD ($)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Changes in the Allowance for Doubtful Accounts [Roll Forward]            
Allowance for doubtful accounts, beginning of period     $ 3,729,000 $ 7,836,000 $ 3,729,000 $ 3,729,000
Charges to costs and expenses       68,000 4,057,000  
Account write-offs and other       (4,088,000) 195,000  
Allowance for doubtful accounts, end of period $ 7,981,000     3,816,000 $ 7,981,000 7,836,000
Loss contingency, additional exposure       0    
Contracts receivable retainage allowances and reserves       $ 422,000   $ 887,000
Minimum            
Changes in the Allowance for Doubtful Accounts [Roll Forward]            
Accounts receivable retainage       5.00%    
Maximum            
Changes in the Allowance for Doubtful Accounts [Roll Forward]            
Accounts receivable retainage       10.00%    
Canada            
Changes in the Allowance for Doubtful Accounts [Roll Forward]            
Allowance for doubtful accounts receivable, period increase   $ 1,934,000        
Accounts receivable            
Changes in the Allowance for Doubtful Accounts [Roll Forward]            
Allowance for doubtful accounts receivable, period increase $ 2,194,000 1,655,000 200,000      
Costs in Excess of Billings            
Changes in the Allowance for Doubtful Accounts [Roll Forward]            
Allowance for doubtful accounts receivable, period increase     476,000      
Construction in Progress, Gross            
Changes in the Allowance for Doubtful Accounts [Roll Forward]            
Allowance for doubtful accounts receivable, period increase     $ 325,000      
Contract Receivable Retainage            
Changes in the Allowance for Doubtful Accounts [Roll Forward]            
Allowance for doubtful accounts receivable, period increase   $ 279,000