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
Jun. 30, 2018
Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Accounts receivable $ 111,178 $ 103,506
Retainage 26,441 26,070
Allowance for doubtful accounts (262) (233)
Accounts receivable, net $ 137,357 $ 129,343