Quarterly report pursuant to Section 13 or 15(d)

Accounts Receivable and Allowance for Doubtful Accounts (Details)

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Accounts Receivable and Allowance for Doubtful Accounts (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Accounts receivable - trade $ 94,614 $ 90,296
Retainage 25,076 23,868
Allowance for doubtful accounts (295) (192)
Accounts receivable, net of allowance for doubtful accounts $ 119,395 $ 113,972